A mate of mine had 18x8 et 20 and 18x9 et22 on his car and could only get away with not rolling the fronts by using a 215/35 tire. He actually used that size on all four corners but the rears needed a mild roll regardless at those specs.
I ended up ordering 215/40's last week to try to see if I can get away with them on coilovers and not touching the fenders. Fronts will be fine, it's the rears I'm just barely unsure of. Will see in the next few weeks.