This is by far one of the best RPGs I've ever played. Of course, I like all the 'games using the Palladium game format, developed by Kevin Simbieda.
If any of you are looking to buy them, most any hobby shop will carry them (maybe not in their entirety).
HERE'S A TIP: If your going to buy any of the Robotech RPGs, buy it along with the corresponding manual. Click here for the home page of Kevin Siembieda, the creator of the Robotech RPG!
These offer character sheets (the Invid Invasion has its own sheets), supporting characters, and detailed information on mecha, vehicles, and other subjects.
If you think that the missions in the Sentinels book are lame too, check out some of the adventures I've developed at this link.
Some modifications to Role Playing Game can be found here.