I will be the minority voice here, but the Roadster is pretty tough to beat. You can be defeated and deflated rather quickly though if you don't take the time to read the amp's manual and factory settings. From there, you can learn to dial in any convincing tone you like, so long as you have the amp running at the proper volume. The Roadster is especially dark sounding and undefined at lower volumes. The Roadster sounds, amazingly, even more clear and defined (especially useful for recording sessions) if the F/X loop is disengaged, a point that Mesa mentions in the manual.
Point in case -- With the Roadster, users can get a pretty convincing array of tones for live settings. The key to the amps channels isn't the gain knob, but the treble, bass, and mids. The Roadster has a huge amount of bass present, something that will require odd settings for many users. Sometimes, depending on the mode and power, it is best to have the bass knob almost off. Pushing up the treble is key in that it adds some gain and brightness to your sound. Having lots of mids is also key to this amp. It is already a super compressed and dark amp. No need to hollow the tone out further by killing the mids. I see people mistakenly trying to brighten a channel by adding presence. I keep the presence low and treble high, then adjust the gain by ear to find the right amount of cut and distortion. No need to look at the knob and feel that you should have it at 2 o'clock. Rule of thumb should be -- use the gain and presence per taste after setting the mids, treble, and bass. Using too much gain or high amounts of gain from the gain knob alone increasingly limits how effective the mid, treble, and bass knobs are at shaping your tone. This is how Mesa sets up their amps. If you understand this, you'll be in good shape. Also, don't the Roadster isn't that great sounding at low volumes. You need it to be pushing considerable power and volume to get the full dynamics out of the amp.
The Roadster is hugely versatile, but it really takes time to learn how to use the amp properly. That is the amp's biggest downfall and a legitimate one at that. Who wants an amp that is that complicated? Most people don't want the hassle. When you plug in to the Roadster, you can get pretty great tones from some of the modes without any extreme settings of the eq. Yet the problem is, you won't get a great sound from all the modes and settings. That is where knowledge of the amps eq and experimentation with your guitar will take players further in discovering the Roadster's total potential. People just have to realize it is darker sounding by nature, while not being a "dark" amp per se. I can't stand seeing people cutting out the mids either. You completely neuter some of the amps settings by doing that. Even on the cleans, where on most amps some prefer a rounder tone, killing the mids on the Roadster hollows out your tone for the worse. The top end and bass on the amp are already massive as is. Adding mids to the Roadster is to the user's advantage, as is keeping the presence nowhere past noon. If the user wants a brighter sound; with more articulation for chording; and clarity and sustain for leads, they will have to employ an unorthodox approach to some of the settings and modes (of which is clearly explained in-depth in the amp's extensive manual).
The Roadster can get you a huge array of kick-ass tones that are convincing if you take the time to learn to amp - this means playing it loud and learning it loud too.
