Congrats on your Mark 5 purchase. I have a Road King II, a Mark V, and an Express 5:50. I can't imagine getting rid of any of them at this point. The Mark 5 does have a very different feel than the Road King II...but I love them all. =D BTW, my Mark 5 was a special order and it was ready in 2 and a half months. My Road King II was ready in 4 months. My dealer always says 4-6 months as a rule of thumb for Mesa though.
So tips for a new Mark 5 owner. Well, unlike the EQ on the Road King which is post gain, the EQ on the Mark 5 is pregain. So, you'll probably want to go a little easy on the bass control. The controls almost feel like it's more subtle tone shaping. The graphic EQ will help a lot....but also try playing with your amp with the EQ off to really learn how to shape your tone with them. Also, the preset contour control is pretty much the classic V shape when you have it cranked up...but the graphic EQ will let you scoop the mids just a little bit more than the preset.
The lead channel on the Mark 5 is extremely fast and detailed. I noticed that when I was recording my Road King and my Mark 5, the Mark 5 is a lot tighter while the Dual Rectifier is a lot spongier. But, the Dual Rectifier has a lot more bottom end than the Mark 5's lead channel.
I noticed you have the Roadster so you know all about the clean channels. Despite the mode names on the Mark 5, they really aren't exactly the same as the Roadster's. I noticed that my fuzz pedals sounds absolutely killer through my Road King II, but I'm not the biggest fan of them on the Mark 5...so try your pedals out and see which amp they go best with.
Best tip for you: Don't sell your Roadster. First, the tone on both are very different. Second off, you'll have a stereo rig if you want. I'm still getting used to the Mark series tone. My first introduction was the Express 5:50. Unlike the Express 5:50 where it's virtually impossible to get a bad tone, the Mark 5 can get awful sounds and great sounds together. It's going to take a really long time to get used to it. I've had mine since mid January and I'm still learning about the Mark 5. In fact, it's hanging by itself right now so I have time to get used to the amp. Anyways, my Dual Rectifier Road King II still blows me off my feet at the end of the day.
The Mark 5 is an amazing amplifier. It is a much tighter, mid-range style kind of amp than the rectifiers are, but it is an amazing player's amp. I don't think I've really reached the full potential on this amp, but it can go from super clean sounds to classic british rock sounds to metallica/megadeth style hard rock. It's got lots of attitude. Anyways, I love my Mark 5 and the rest of my Mesa collection.