Owning both a Peavey 6505+ and a Roadster, I can undertand the original thread posters situation somewhat.
The way the Peavey is voiced it just dominates and cuts through like a mofo with a ton of high end and controlled chunk, and you need to set a more smooth and lower mid based amp like a Recto's tone stack in a way to carve out your own sonic space and not directly compete with the Peavey's, a battle which you will lose imo.
But even in that situation the Mesa will tend to occupy a lower sonic space than the Peavey and your ears may still perceive that as not competing against it well.
I've always avoided two guitarist bands whenever possible because of the additional complexity of making sure whatever amp I'm using will mesh well and won't be lost in the mix against what the other guitarist is using.
I love Recto's for one guitarist bands because they have a huge sonic footprint and fill alot of space. In a two guitarist band I might choose an amp that is more focused and cutting that occupies less sonic space, but has the advantage of slicing through better.
That is just me though, and one of the reasons I like to have a few different amps around is so I can choose the best tool for the situation at hand.
If I joined a band and the other guitarist had a 6505+, my Roadster would probably not be my first choice of amplifier. I would probably reach for my Marshall 2203 JCM 800 or Splawn Nitro (either of which could easily give the Peavey a run for it's money cutting through the mix imo
) or even my own 6505+ lol. :lol:
I do love my Roadster though, don't get me wrong. I just like to use it in situations where I think it can shine the best...but if you don't have multiple amps to choose from and need to make the Recto work I'm sure throwing a graphic EQ in the loop with some tweaking would definitely help you compete against the Peavey better.
The Roadster is the darker and smoother amp of the Recto line however, so it would actually be at more of a disadvantage against a Peavey 6505+ than a Regular Dual or Triple Rec imo. The Triple Rec is the most aggressive/tight of the entire line that I've played personally, so I can understand the guy above with the Triple that says he has no problem against the 5150. The 5150 II/6505+ are voiced higher in the mids than the 5150/6505 which are another factor as well to consider.
Good luck.