Choosing pot size after removing compacted nursery soil

I removed a thick plug of compacted nursery mix from a new plant and discovered more roots than expected. The root mass fits its old pot once loosened, but a few thick roots circle the bottom. I'm undecided about going up a pot size right away: too large could leave wet soil around the roots, too small means repotting again soon. How do you judge size after teasing out nursery soil without overpotting?