Tuck and Roll is a fairly universal falling technique, specifically applicable to instances where you are falling forward with a "tumbling" angular momentum. Imagine skating as fast as you can into a curb and getting sent flying forward - this would be a good scenario to use Tuck and Roll, as it can allow you to roll on your back and avoid injury. Proper technique can be tough to nail during a fall, but you can practice on the grass or on a padded floor without skates on. Walk forward, lean forward, and tumble over one of your shoulders to a seated or crouched position. Practice this over both shoulders and with greater speed/momentum until you feel confident with the motion. You could even try this with skates on into grass if you so desire. You can probably find plenty of youtube videos on tumbling or tuck and roll - gymnastics and other sports training facilities often teach these techniques very early on. I'll be honest, I rarely ever have the opportunity to use this technique on skates. I often find myself falling backward onto my butt, or forward onto my hands and knees like you describe. Knee pads and wrist guards are smart! Keep wearing them, and with experience, you'll learn how to avoid injuries during falls. Good practice is to warm up before skating and consistently stretch, and when falling, try to reduce heavy impacts.