For a clockwise barrel roll, do the following movements while skating along the line:
Start by skating on your left foot going forwards along the line.
Now skate your right foot forwards from behind the left foot, transferring your weight to it.
Now place your left foot, pointing backwards, behind your right foot, heel to heel. This is simply a front to back transition.
Transfer your weight to your left foot, skating backwards.
Put your right foot down, and lift your left foot up.
Again transition to skating forwards by putting your left foot down in front of your right foot.
You have just completed one full cycle of the barrel roll. Continue practicing this along a straight line, and very soon you will have the series smooth and controlled enough to be able to start doing it on a circle!
Some tricks to speed up and smooth out the barrel roll
How to make your moves more smoothly:
Bend your knees as much as you can. Your knee should be well over your toes - at least two inches in front.
Be sure not to look down at your feet.
Slow down your movements at first, until you can prolong each stroke. Once you're confident, then look at speeding up the move, not before! This way you will end up with much better balance and control.
Speeding up and tightening the barrel roll:
Try to keep the rotation of your shoulders at a constant rate, matched to the movements of your feet.
Turn quickly while doing the barrel roll, thus making lots of quick foot movements. Remember that this is a dynamic move, and it's important to turn fast for the move to look good.
Once you start to practice this move in a circle, try to kick your feet down onto the short line each foot makes, and through to the upstroke. Short, choppy movements will help you to speed up the barrel roll.
Keep your outside shoulder high, and your inside shoulder low. As you rotate you'll have to keep changing the high shoulder, and this will help increase your lean into the big circle.
Do it both ways:
Be sure to practice this skill in both directions - not very many people can do it in both directions, and what could be cooler than doing a barrel roll for an entire circle to the left, and then reversing your rotation and doing another circle to the right.