In dynasty leagues with good size farm rosters they're worth picking up and stashing and watching. In seriously deep leagues they might even be bench depth, but with the forward talent the Stars have their ceilings are pretty low, making them more likely to serve as injury fill-ins. That really depends on league depth though.
Garbutt is more offensive-minded and Roussel is more of an agitator. Garbutt did show some offense in the AHL, posting a roughly .6 pts/gm pace. I'm not sure he'll post that in the NHL, and even if he did he's still buried on the depth chart.
Roussel did post some decent offensive numbers in the QMJHL, but that hasn't translated to the pros, though he is having his best season offensively speaking this year with the Texas Stars, 19 points in 43 games. His calling card is PIMs though, and lots of them. In 146 career AHL games he has 372 PIM. The downside of that calling card is taking bad penalties, and it's already earned him one demotion back to Austin.
I'd say these guys are farm material in most leagues right now. Garbutt has the advantage as he sees more consistent playing time and has a small amount of offensive upside. Roussel could be a deep sleeper for peripherals if he can cut down on the stupid penalties that put him in the doghouse.
Your beer mug isn't half-empty, your just half-way to the next refill.....