Gracie,
Hmm, I'm not sure I can describe it but I'll try.
The key to really good body rolls is isolations...meaning you need to use each part of your body in isolation from the rest of it to make it look like a ripple or wave is progressing through your body. Body rolls can start low and go up, or start at your head and go down. You can roll forward from a body position behind your leading foot, or back from a body position ahead of a trailing foot, or sideways in either direction.
You start with your weight solidly on your standing leg and will progress towards the (ooh, rats, where's that proper term when I need it) 'other' foot in the direction of the other foot and end up on the last count with all your weight on the other foot. You can do body rolls without a weight change too, but it's a little harder to learn that way because the motion is not as pronounced. The replacement step body roll I suggest below works that way, with the step after the roll.
Since you are wanting to put this in context, here are some suggestions for moves that use body rolls:
If you have a move that puts you in a bowtie position (side by side with lady's L arm across man's shoulders, man's R arm around lady's back, lady's feet together or with weight on L foot and R foot to side) you can (each) do a side body roll out of it. Starting in the bowtie, imagine a hole in a wall on your R side. There is an invisible glass wall on the other side of the hole that you are going to line the R side of your body up against. You are going to crawl through the hole one part at a time. Tip your head over to go through the hole. As you straighten your head on the other side (line up with the glass wall and bring the rest of you along it in alignment), bend your upper spine to take your shoulders through the hole. Straighten your shoulders and bend your waist to take your hips through. As your hips come through, take weight on your R foot to finish (you should end up with your body upright along the glass wall over your R foot, L foot still in place where you started from). Like I said, it is key to isolate the movement. Once you have straightened, don't tip your head or shoulders back to the left, keep them straight on the glass wall. Try this in front of a mirror to see what works. You can use any number of even counts to get there depending on how fast you can do it.
BTW, to go to the next move, your partner will have to lead you forward on the "and" count to get your weight back on your left foot before you can step forward with your R foot on 1.
In case you don't have a bowtie move, you could do forward body rolls with a replacement step on an underarm turn variation using 10 or 12 counts instead of the usual 8. I'm not sure I can explain that, but perhaps you can play around with it using the sideways imagery. The replacement step switches the weighted foot back so you can keep going.
Another cool body roll move would be on a tuck turn. Do 1, 2, then on 3 face your partner weight forward on R foot, L foot back, double hand hold (note: again, both partners will roll, but I'm only giving the lady's part). In this case, your L heel is at the base of the glass wall that you will roll back against starting with your head. Tip your head back, straighten head OVER YOUR L FOOT WITHOUT CHANGING WEIGHT -- Important! You must already be at the glass wall when your head straightens, but your CENTER should still be over your R foot. Obviously, you can't leave your L foot too far behind or this will be very difficult. You will be in a weird curvy shape at this point (if you stop here). Roll your shoulders and back straight on the wall, then bring your center (hips) and change weight all at once ("plop"). Your L knee will be bent and your R knee straight. To roll back up, do a pelvic thrust forward, then roll up your body and end with your head over your R foot (in this case you will change weight gradually on the way up). You can do this fast -- 3, down on 4, up on 5, 6; or, down 4, 5, 6 up 7, 8. The last two counts should be something along the lines of: step L down the slot on 7, turn to face partner on 8 (no weight change on 8).
Whew!
I don't know if you'll be able to figure any of that out without seeing it, but you can try it just for fun. I don't know how popular body rolls are for ballroom comps, but they are huge right now for country and social dancing.

[This message has been edited by Belle (edited 08-10-2000).]