Db : 8.0.6

I have a database that has just one application schema. All it contains is some 400 snapshots to a master database. Don't go by the number, all these snapshots get refreshed 'COMPLETE'ly every night and it takes about 7 minutes. Real small tables.

These are not updatable snapshots.

Now, given the fact that I have only this one application schema in the database, the snapshots are not updatable and they get refreshed once every night, I expect to see no rollback segment activity. At least pretty low, correct ?

On the contrary, I am seeing the rollback WRITES incrementing continuously. I can not see any transactions in the database. Just SELECTs. v$transaction, v$open_cursor are always empty. I don't even see archive logs getting generated frequently.

Someone is telling me the db might be suffering from WAITS on rollback segments. My question is WHY - when noone supposed to 'write' anything to this db ?

Is there a way to find out who is using the rollback segments in this scenario and for what ? Which processes should I expect to be using rollbacks ?