We have only 2 Sifrei Torah available instead of 3 for Shabbat Rosh Hodesh Parshat Hachodesh. The first Torah is already rolled to the correct weekly parsha (let's assume it's this year, so it's at Vayikra).
I am going to make a general assumption that we want to do as little Tircha D'Tzibbur ("congregational burdening") as possible, so we want to roll the Torah as little as we can. This is what I shall use in each of these scenarios. If my assumption is incorrect, please indicate what to do and why.
- 2nd Torah rolled to Pinchas for Rosh Hodesh. Do Hagbah on 1st, use 2nd for Rosh Hodesh, Kaddish - do Hagbah on 2nd, re-use 1st and roll back to parshat Bo; do Hagbah again on the 1st.
- 2nd Torah rolled to Bo (for Hachodesh). Roll 1st Torah to Pinchas, read for Rosh Hodesh - Kaddish, Hagbah on 1st; read from 2nd, Hagbah.
- 2nd Torah rolled to parshat R'eh (it hasn't been used since Shmini Atzeret. It's about the same distance from R'eh to Pinchas as it is from Trumah to Pinchas). Hagbah on 1st. Roll 2nd to Pinchas - Kaddish; Hagbah; Re-use 1st, roll to Bo; Hagbah again on 1st.
In answering this question, you may want to refer to this related M.Y. question