Check both sides of the new disc to see if the bolt boles are counter-bored (recessed) on one side - if they are, this in the side that the bolt head sits in so it faces away from the wheel. This might sound obvious but ten years ago I bought a ZX-9R from a muppet who worked at MCN and he'd refitted the rear disc the wrong way so the bolt heads were proud and they fouled the calliper bracket badly. It would have been impossible to rotate the wheel or push the bike anywhere as the foul condition was that bad so what had he done? Simply ridden it like it and the bolt heads had chewed themselves some clearance into the bracket. I couldn't believe what I was seeing when I discovered it. Anthony Orfeo, hang your head in shame...
Another important point; use a good hex drive bit on a socket to remove the disc bolts and ensure that it's fully engaged before trying to turn it. Chewed-up bolt heads are never easy to remove, especially when thread-locked in. It isn't necessary to replace the bolts, up to you if you want to but if they're undamaged they can be re-used (with thread-lock)
