rear wheel/rotor question

You could bend it back, or get a new rotor...you could ride with it like it is, but you may get grabby rear breaking and wear pads quicker than normal....good luck with it.

Not much really, I rode/race my lil bro's RM 125 with a slightly bent front rotor non floating mind you. I'd recommend fixing it or getting a new rotor asap though, it will cause the front end to drop when jumping it's going to act like your tapping the brake.

Well rear disc's brakes are non floating, usually front disc brakes are floating mainly on yz's and KX's. What it allows the disc to do is if it's bent slightly or wrapped it allows some side to side or freeplay if you will in the caliper it usually move's on the disc area it's self. You've seen how on yz's and kx's where the disc bolts to the hub and then there's the rivots above it slightly it moves there but only a tiny bit. The concept is to create less drag if that happens. You can take off the disc and straighten it out but do so on a very flat even surface! Take extreme care in doing this it's very easy to make it worse, do not just eye ball it you must measure it. Think of it as if you where trying to true a rim .5 a mm off should be okay. I should ask what my friend does to fix'em but he does have a wheel truing stand.