i am going to buy 4 Rock Crawler rims. i know i will get 15x8's. however, what backspacing should i get? also, is my bolt pattern 5 on 4.5? if not what is it? thanks

Yes the bolt pattern is 5x4.5. I used 15x8's with 4" of backspacing with 33x12.5 tires. Worked great.
Nathan