There's a good write-up here about rolling. See below: http://www.europeancarweb.com/tech/techlet...techletters02e/
The text below is an excerpt from the page above. Hope it helps a little as it does describe the fender rolling process.
It's titled 'Wheel/Tire Fitment for an E36 M3'
"...8.5x18-in. wheel is too wide for the front of an E36 M3, and too wide for 225/40ZR-18 tires. Optimally, you would want an 7.5x18-in. wheel at the front. However, you don't mention what offsets these wheels are, and that is key. Without that information, we can't speculate on whether you would need spacers or what size spacers might work.
Now, on to the rear tires. Just because a given size tire will physically fit on the car, does not mean it's a good idea. If the look is all you care about, that's one thing, but with that much size difference between the front and rear tires, this M3 is probably going to understeer like a 1980 Chevy Citation.
For the benefit of anyone doing it or needing it done, now would be a good time to talk about rolling fender lips: The conventional way to roll fender lips is with a wooden baseball bat--preferably a miniature Louisville Slugger, or with the handle end of a regular bat. A wooden dowel rod from Home Depot will also work, and is actually a better idea as the job may ruin the baseball bat.
First, the tech will jack up the car, remove the tires and thoroughly clean the backside of the work area with a wire brush and solvent. Then, he'll refit the wheels, lower the car, drive it to settle the suspension and use a heat gun to soften the paint in the rolling area. The bat gets wedged in place, and the car is gently rolled forward or back by hand while a helper keeps the bat in position manually. After the roll is complete, a good tech will again lift the car and remove the wheels--this time to apply a coat of zinc primer to the back of the rolled area in case any paint cracking occurred, followed by a bead of caulk-gun type automotive seam sealer to the entire groove created by the roll. A quick swipe with the thumb, wait for the seam sealer to dry, finish with a quick spray of paint and you're done. Failure to do the last steps can result in body rust due to road schmutz laying in the groove.
The high-tech way of rolling fender lips employs a special tool that bolts to the hub and uses a soft roller to effect the modification. The Tire Rack has or shortly will have this tool available for rent or purchase.
Either way, two simple caveats apply to fender rolling. First, if you're not sure whether you have body filler in the fender lip area, you need to have the tech check for it before attempting to roll the lips. Body filler (Bondo) in this area will always crack when you try to roll the lips. Second, although paint rarely cracks during the job if you soften it with a heat gun, no one can promise this. It is a possibility you need to be ready for. "