Megillah 32a says:
עשרה שקראו בתורה הגולל ספר תורה קיבל שכר כולן
If ten have read from the Torah (meaning that at least ten verses have been read; not that there was a minyan of at least 10 people or that there were 10 aliyot. See Rash"i, there), the one who rolls it up receives the reward of all of them.
(Edited with thanks to DoubleAA & YehudaW providing me some historical context)
As there were no "poles" (atzei chayim) during the time of the Gemarah, it makes sens that one person did both lifting and rolling. This was called just gollel.
At what point and for what reason was what we now call hagba - "lifting" added? Was it added at the time that the poles were attached, and was it mainly for that reason? Related - when / why were the poles used? Even after their attachment, initially, did one person do both or were the jobs separated?