I did none at all. I don't think the early rolling had anything to do with the in tummy time. I am small and my belly was very tight with all three kids. I put on very little weight and my babies were all very squashed inside. They gave up moving well before birth. I even had some trips to the hospital to make sure they were still alive because they stopped kicking.
I put the early rolling down to having lots of unrestricted time on the floor. On a good soft but solid surface. I was often lying on the floor with my babies and I always sat on the floor with them rather than the couch.
They also had cloth nappies most of the time which are bulkier, I don't know if that helped or hindered though. I held them for feeding, stories, and time on the swing. ( yes I was a adult with my very own swing, it was a gift from a kind friend
) but I think they got more floor time than most kids. I didn't own one of those baby seats or bouncers