Roland did make a Super Cube 100 for bass.The Fender Frontman 15b is definitely a bass amp, although less powerful than the Cube. Fender made a Frontman 15 for guitar and the 15B for bass.
If the Roland is the bass version, grab it. They make great stuff. I have a Roland CB100 Cube that I use for most gigs these days. They're really versatile dependable amps.
Sadowsky club member 53