The Darkei Moshe (Rema) Orach CHaim 475,10 gives the final verdict:

כתב מהרי"ו בדרשותיו שצריך לצלות הזרוע והביצה מבע"י דהואיל שאינו אוכלו בי"ט אסור לצלותו בי"ט ונראה דאם רוצה לאכלו בי"ט ראשון ולעשות אחרות לליל י"ט שני דרשות בידו ואז יוכל לצלות אף בי"ט הואיל שאכלו באותו יום ולא כתב מהרי"ו אלא לפי המנהג שנוהגים להשהותו עד ליל ב':
The Mahariv says one should roast the meat on the bone and the egg during the day before Yom Tov since one does not eat the meat on the bone rather he keeps them till the second night of Seder to use again (it is forbidden to cook from one day of Yomtov for the sake of the next day unless its Shabbos where one requires an Eruv Tavshilin).
But it seems that as long as one intends to eat the meat of the bone or the egg during that Yom tov day's meal (As the meat which is roasted one should avoid eating on seder night as noted Shulchan Aruch 476,2) one can roast the bone with its meat on Seder night as one will eat it on the same day as it was cooked. One can then roast another bone with meat on the second night of seder for usage during Seder as one of the two cooked foods as long as he eats it the next day for the second Yom tov day meal. Even the Mahariv would have agreed to this had the minhag in his place not been to keep the same zeroa for both days.

• So when cooking Zeroa on Pesach night one must eat it the next day and make a new one on second night of seder.
• But if one cooks the zeroa on the day before Pesach one does not need to eat the bone meat rather keep it for both Seder nights and optionally eat it during the second day meal.
• Note: The bone should have meat as the Darkei Moshe ibid, 8 says עצם בלא בשר לא מיקרי תבשיל לכן צריך שיהא מעט בשר סריך עליו

The Darkei Moshe (Rema) Orach CHaim 475,10 writes about the zeroa see points below for summary:

כתב מהרי"ו בדרשותיו שצריך לצלות הזרוע והביצה מבע"י דהואיל שאינו אוכלו בי"ט אסור לצלותו בי"ט ונראה דאם רוצה לאכלו בי"ט ראשון ולעשות אחרות לליל י"ט שני דרשות בידו ואז יוכל לצלות אף בי"ט הואיל שאכלו באותו יום ולא כתב מהרי"ו אלא לפי המנהג שנוהגים להשהותו עד ליל ב':
The Mahari veill says one should roast the meat on the bone and the egg during the day before Yom Tov since one does not eat the meat on the bone rather he keeps them till the second night of Seder to use again (it is forbidden to cook from one day of Yomtov for the sake of the next day unless its Shabbos where one requires an Eruv Tavshilin).
But it seems that as long as one intends to eat the meat of the bone or the egg during that Yom tov day's meal (As the meat which is roasted one should avoid eating on seder night as noted Shulchan Aruch 476,2) one can roast the bone with its meat on Seder night as one will eat it on the same day as it was cooked. One can then roast another bone with meat on the second night of seder for usage during Seder as one of the two cooked foods as long as he eats it the next day for the second Yom tov day meal. Even the Mahariv would have agreed to this had the minhag in his place not been to keep the same zeroa for both days.

• So when cooking Zeroa on Pesach night one must eat it the next day and make a new one on second night of seder.
• But if one cooks the zeroa on the day before Pesach one does not need to eat the bone meat rather keep it for both Seder nights and optionally eat it during the second day meal.
• Note: The bone should have meat as the Darkei Moshe ibid, 8 says עצם בלא בשר לא מיקרי תבשיל לכן צריך שיהא מעט בשר סריך עליו

The Darkei Moshe (Rema) Orach CHaim 475,10 gives the final verdict:

כתב מהרי"ו בדרשותיו שצריך לצלות הזרוע והביצה מבע"י דהואיל שאינו אוכלו בי"ט אסור לצלותו בי"ט ונראה דאם רוצה לאכלו בי"ט ראשון ולעשות אחרות לליל י"ט שני דרשות בידו ואז יוכל לצלות אף בי"ט הואיל שאכלו באותו יום ולא כתב מהרי"ו אלא לפי המנהג שנוהגים להשהותו עד ליל ב':
The Mahariv says one should roast the meat on the bone and the egg during the day before Yom Tov since one does not eat the meat on the bone rather he keeps them till the second night of Seder to use again (it is forbidden to cook from one day of Yomtov for the sake of the next day unless its Shabbos where one requires an Eruv Tavshilin).
But it seems that as long as one intends to eat the meat of the bone or the egg during that Yom tov day's meal (As the meat which is roasted one should avoid eating on seder night as noted Shulchan Aruch 476,2) one can roast the bone with its meat on Seder night as one will eat it on the same day as it was cooked. One can then roast another bone on the second night of seder for usage during Seder as one of the two cooked foods as long as he eats it the next day for the second Yom tov day meal. Even the Mahariv would have agree to this had the minhag in his place not been to keep the same zeroa for both days.

The Darkei Moshe (Rema) Orach CHaim 475,10 gives the final verdict:

כתב מהרי"ו בדרשותיו שצריך לצלות הזרוע והביצה מבע"י דהואיל שאינו אוכלו בי"ט אסור לצלותו בי"ט ונראה דאם רוצה לאכלו בי"ט ראשון ולעשות אחרות לליל י"ט שני דרשות בידו ואז יוכל לצלות אף בי"ט הואיל שאכלו באותו יום ולא כתב מהרי"ו אלא לפי המנהג שנוהגים להשהותו עד ליל ב':
The Mahariv says one should roast the meat on the bone and the egg during the day before Yom Tov since one does not eat the meat on the bone rather he keeps them till the second night of Seder to use again (it is forbidden to cook from one day of Yomtov for the sake of the next day unless its Shabbos where one requires an Eruv Tavshilin).
But it seems that as long as one intends to eat the meat of the bone or the egg during that Yom tov day's meal (As the meat which is roasted one should avoid eating on seder night as noted Shulchan Aruch 476,2) one can roast the bone with its meat on Seder night as one will eat it on the same day as it was cooked. One can then roast another bone with meat on the second night of seder for usage during Seder as one of the two cooked foods as long as he eats it the next day for the second Yom tov day meal. Even the Mahariv would have agreed to this had the minhag in his place not been to keep the same zeroa for both days.

• So when cooking Zeroa on Pesach night one must eat it the next day and make a new one on second night of seder.
• But if one cooks the zeroa on the day before Pesach one does not need to eat the bone meat rather keep it for both Seder nights and optionally eat it during the second day meal.
• Note: The bone should have meat as the Darkei Moshe ibid, 8 says עצם בלא בשר לא מיקרי תבשיל לכן צריך שיהא מעט בשר סריך עליו