I got a Roadster head about 6 months ago.
At first, I was really happy, coming from a single channel Marshall. The cleans on the Roadster blew me away, and I figured I could find a dirty tone somehow.
For dirty tones, I initially tried the Spongy/variac mode. I could not find a setting that knocked me out. I turned up the gain and used modern...buzzy. Next I tried Raw with the gain full up, and that was dull and buzzy at the same time. I introduced a BB+ to the mix, and I got a little closer to acceptable.
I became really disillusioned that I had this high gain monster, but I needed a drive pedal to make it acceptable. I was convinced I had to sell it.
I drove down to the music store and tried a Royal Atlantic, and I liked it a lot. I tried a Marshall JVM410H, it had a good plexi sound on channel 2 orange mode, and there were plenty of options, like speaker voiced line out, midi etc. Not bad. But I had Marshalls for years....lastly I plugged in an Orange OR15 head. Wow! If that was a little louder, and had 2 channels....it could be a winner! I tried the EVH too...it was alright, but somehow it felt hair band-like....if that makes sense. Lots of sizzle, no steak?
I decided to give the Roadster another kick at the can. I used channel 4 in Vintage mode (100 watt), with the gain around 1-2 o'clock. With the master up around 11 o'clock....it sounded thick, responsive, and percussive. So, I tried Ch3 in Vintage (50 watt), I tried an old favorite setting, treble 0, mids and bass pretty much cranked and presence way way down. Not bad! A little tweaking and that could be a useful channel.
I have played live twice with these settings and rehearsed numerous times. Throwing in the BB+ to kiss the preamp a little on the occasions when a touch more glue is required....I am getting pretty close to being satisfied. I still find the attack a little over emphasized at times on single notes...but I am confident I can work my way around this with tweaks to tone knobs and picking technique.
In the end, it takes some help from the power tubes, because the pre amp gain alone is not satisfying to someone that likes Michael Landau, Robben Ford, Jimmy Herring, hell even Gary Moore. You need to turn the pre amp gain down a touch, and get those power tubes to start cooking.
To get this at lower volumes.....maybe the Rivera Rockcrusher Recording is an option. $800...but looks promising.
Live with it, try it in various situations...and if it just cannot get you where you want, sell it. There are lots of options.
p.s. if you like boutique style Marshall's....I was REALLY impressed with the Third Power RPO100.