There doesn't have to be any neg G's in the aileron roll. It depends on
how high you start your pitch attitude and how slow the plane rolls. In
the Decathlon I'd just pitch up 30 degrees and throw the stick to the
left. At the end I was mostly zero pitch and never had to put any neg
Gs in (although you can if you'd like). A C-150 probably rolls slower
any may require less than 1 G (say 0.5 Gs) to prevent excessive nose
down, I'm not sure.

-Robert