All amps have a baked in tonal *range*, which may be wide or narrow, deep or shallow, etc. It really just comes down to what you like. Even if you set preamp EQ flat on a given amp, the circuit designer made voicing choices in the rest of the preamp, power amp, cab sims if included, etc. That voicing can be anywhere from more or less transparent to sounding like an SVT stack, a Marshall stack, a Fender Bassman, etc. The Rumble tends toward a Fendery sound, IMO, but (a) it's not a clone of any of the old fender tube amps (I'm not really familiar with their other solid state offerings), and (b) there's a lot of variation in the amp's tone, based on where you point the knobs, your bass, how you play, etc. It's definitely not a one trick pony.
That said, some people prefer other things. Ampeg devotees, for example. (I happen to like both[1].) If at all possible, try a Rumble and compare it against other offerings, as @SoulReflection suggested. Or get one from a retailer (local, net, whatever) that has a good return policy, and play as much as you can with it for a week or two, ideally with a band part of the time.
[1] While I won't claim to get an Ampeg sound out of a Rumble, I will say I can get close enough for my purposes. I can't play nearly as well as any of my heroes, but I can get a wide variety of tones out of my Rumbles, including the Ox, Felix Pappalardi, Jack Bruce, Berry Oakley, and more. I can make it sound like an old Motown bass rig.