Front 19x9.5 +12
Rear 19x10.5 +12
What would the best tire size for these rims with minimal fender rolling?

 

With those wheel offsets, the usual 245/35 & 275/35 combination should work fine (OR 255/285) but either one, 90% probability of needing to roll the rears if lowered (even minimally). Stock height might clear. Lot depends on your shocks/springs/camber.

 

If you go with the smaller size from Mic’s suggestions (245/35 & 275/35), and you keep the stock suspension, you might not need to roll the rear fenders. I went with 245/40 and 275/40 on 18” wheels with a 15 offset, dropped the car 0.5 inch, and did not need to roll the rear fenders.

BTW: There is not such a thing as “minimal fender rolling.” Either you roll or not.