First: It's not a role-playing game. At all. It's about half space sim, half real-time strategy. And it's all multiplayer: the only non-humans in the game are things like construction and mining ships. There's not really any plot and almost no opportunity to play "against the computer."
Second: It's extremely fun, the most intense fun I think I've ever had in an online game (including Freelancer). Between the team, you need to escort miners and constructors, attack the ones that belong to the enemy, deploy early-warning probes so that you know when enemy ships are near, research new technology and build new bases, stop enemy bomb runs, organize your own bomb runs, guard chokepoints on the map, break through guarded checkpoints, scout out the opposition, lay down mines to stop enemy advances, use special stealth units to attack miners and bases, hunt down enemy stealth units with scouts...
Third: It has a pretty steep learning curve. This curve is eased by the wealth of information available for learning the game. Learning to fly doesn't take too long, especially if you have much space sim experience. What takes a while is learning to work with your team to carry out the wide variety of tactics and strategies that get employed. It will take a month or two to be basically "literate" as a player.
I recommend it. I play Alleg to satisfy my action/tactics/dogfighting itches, and Freelancer for roleplaying.