I have a 3ch Dual Rec I'm very happy with but like you, I occasionally get the urge to 'hear' something different. My DR has been modded by Voodoo amps so it is probably closer to a Roadster for comparison. FTR I have owned a Mark IV.
The front end:
The recommendations above are the best ones for Mesas. I own a few good OD pedals I run in front of my DR that help to get certain 'tonal flavors' that are difficult to get with the amp by itself. I typically use a TC Electronics chorus pedal as the first pedal in front of the amp. This is an A/C pedal that changes the input to Low Z allowing me to have a longer cable run, minimizing fidelity loss and maximizing harmonic content.
The loop:
I prefer delay to reverb and use a DD-6 and a Carbon Copy, as needed. I own a MXR 10 band GEQ that I run in the loop to get a real close SLO sound. You get a different tone/gain level from using the Solo function and/or turning the loop off. There is more available gain with the loop in as the effects loop is buffered with a tube circuit with send and receive attenuation available.
The speakers:
Depending on the cab type, number of speakers, speaker model/manufacturer and input impedence, you are going to get different sounds, sonic effect. I have open and closed back cabs. 1x12s, 2x12s, and 4x12s in 8ohm and 16ohm varieties. I recently have been drawn to head/cab setups over combos for this very reason. If I want to try something different I only have to plug the head into a different cab instead of swapping out speakers. An old EV 12L Thiele cab has a much different tone than does a 4x12 standard cab of Vintage 30s, both being great choices for a Recto or Mark series amp.
And last but not least....
I recently had the chance to but a Blue Stripe Mark III rackmount for a very good price. It needed work but was basically a solid amp. It is a Simul-Class unit with a Graphic and Reverb. I was going to fix it up and sell it to fund some future but yet undetermined GAS but after I was done with it did not have the heart to sell it. I had forgotten how much different the Marks and the Recto were. I have an old DOD A/B stomp box that I used to have both amps available at the same time and spent the entire afternoon switching back and forth playing every song I could think of from Metallica to Dreamtheater to Allman Bros to Eric Johnson, etc, etc, etc.
For the Record,
I have been a Mesa owner for over twenty years. I've own one or more of most of their major product lines. I have bought and regretted the purchase with some of their amps. I have sold and regretted the sale of a few of their amps. I can tell you amps are like people and guitars and cars and anything else. Just because they have the same name of the chassis doesn't mean they are all created equal. There are good ones and not so good ones. I cannot give a quick explanation why that is, you just have to play a bunch of them to realize this.
You cannot go wrong with any Recto for 'that sound', if that is what you are looking for. I would wager that the Dual Rec is probably one of the single most recorded amplifiers in Rock history. The Roadster is a well thought out Rock amp and is the next logical evolution of the Dual Rec with only a few options short of the Road King. Great cleans, medium gain sounds and all out mayheim are available in an intelligent package that is hard to beat for the money.
The Mark series are the amps that started the 'Hot Rodded to the Public' amp phase that grew into the current 'Channel Switcher' paradymn that we now consider the norm for almost any musical genre. Mark I, IIc+, III, IV and now the V have and always will be great amps. I think they have better cleans than most the Rectos, (maybe not better than the Lonestar or Road King). For shredding there is an urgency with the Mark tone that just works very well for single note articulation. You can get a Mark to sort of sound like a Marshall or Fender or ???, but it won't sound like a Recto and vice versa.
Bottom line,
At the end of the day, though, they are Mesa amps and they sound like a Mesa to me. I don't think most folks can tell all of the differences on the recordings or sound bites unless they are guitar players and have played the amps that are listed on the band's website, but I could be wrong. I remember the first time I heard a Soldano SLO and realized that that was the amp that made 'that' tone. Rat, the Allman Bros, Sambora, Van Halen, Clapton, etc, have all played this amp. While I honestly think the tone these guys produce is magical I also think they could probably pull most of it off with a Pod or ProTools direct into the board. Again, I could be wrong. I think we all Jones about owning 'the' amp that will give us the magic not realizing that we as musicians hear the magic more than the non-musicians all the time, whether it is coming from our guitars or someone elses. I own a Bad Cat and a Cornford that don't sound like my Mesas but I won't be selling either of these amps either for the 'magic' that they can do any time soon as well. I know that most older players have figured this out and thus own more than a single amp for this specific reason. Plus it is just easier to just plug into a different amp once in a while to revitalize your playing than to go 'on the hunt' for a new amp when you are weary of the tone you are getting from your 'main amp'. YMMV
My advice:
IF the Roadster is a good deal AND it sounds good to you, buy it. For that sound, only a Recto does it best.
In a year or two after all the bugs have been worked out, start looking for a Mark V to buy. I'm very comfortable in buying used because Mesa amps typically last a long time.
In the mean time, if you want to have that Vintage Mesa sound, look for a Mark III. They are selling for a good price right now by all the guys that want to be on the 6 month waiting list for a Mark V.
cheers
