I would not cut any more roots. If there are any girdling roots (going around and around) they could have been teased out from the rootball and it sounds like you did that, but cutting the roots has likely reduced the amount of root that can supply water to the top growth. The plant's reaction may be to drop some of the leaves so that the tree needs to take up less water for transpiration.
Having said that, it's not totally unusual for even established honeylocusts to get a few yellowing leaflets, especially going towards fall. I would keep it watered to compensate for the root loss but don't get the soil too waterlogged, and don't disturb it further, leave the roots alone. They're pretty tough plants, there are a lot around here and we have one in our front yard.
