non-m fitment

Have an 03 325ci with TMS Tracksport Coilovers.

I was looking into wheels and found a set 19x8.5 et 40 19x9.5 et 22... I know the rears are really aggressive, but with what would I have to do to make them fit? Just rolling the fenders or would I need to stretch the tires as well?

It's pretty hard to say exactly what is needed in order to make those fit... Some tires run wide, some run narrow, some run tall, some run short, etc.

Your ride height, alignment specs, tire brand/model, tire size, and fender work all play a part. A good amount of fender work will be needed, it just depends on all the other factors coming together.