In ice hockey from time to time I take a puck or stick to an exposed area of my upper body, and was looking for a base layer that provided a bit of padding to supplement my shoulder pads.
The Reebok 7K padded shirt is extremely light. It's obviously a bit heavier than a traditional base-layer, but it's astonishingly lightweight given all of the padding it has. The upper chest is hard HD foam, and the rest of the shirt is single density foam. Worn by itself, it provides more than enough padding for roller hockey, and when used in conjuction with shoulder pads it offers a great level of additional protection without adding bulk.
My only issue with the 7K padded shirt is that it gets hot. The "play dry" material of which the shirt is composed is nothing like other base layer shirts. It reminds me almost of those see-through sleeveless jerseys you had to wear in gym class. It is perforated and breaths, but it does not keep you cool the way say an under armour shirt would. Even for ice hockey, it does trap more heat than I'd like, but the occasional squirt of water down the chest/back counteracts it sufficiently.
The Reebok 7K padded shirt will give you good protection at a fair price, just keep a cold waterbottle around to keep cool.