Softail,
This sounds great, as you've got a varied enough equipment background to understand my thoughts.
The RK is a high-end amplifier, that's part of the Recto product line. First and foremost, it excels at being a Recto.
With that being said, it's very versatile as you suggested.
While the product description includes "Improved Channel 1 & 2 now features CLEAN and FAT from our acclaimed LoneStar" (btw, I don't believe the LoneStar has a 'Fat' mode, lol), you have to take this with realistic expectations. If you go into it believing that the RK has 'nailed' the LS sound via a 'cut & paste' from that amp, you're likely to be disappointed. It is certainly a VERY usable clean that makes the most of 'lessons learned' and circuitry inspired/lifted from the LS at all possible points. I'll leave it for a true LS user to give the rest of the input from their experiences.
At the end of the day, if you think of the amp as the highest level of 'Swiss Army Knife' of the Mesa Rectifier line, you won't be disappointed. If you go into the purchase/use of the amp thinking of it as the highest level of 'Swiss Army Knife' of all amps, your experience may leave you disappointed.
This being said, if users also speak up with their Roadster experience, by all means consider it valid. As you're probably aware, the differences are 1) No cab switching AND 2) can not use a combo of 6L6 and EL34 in the same sitting. Also, I believe the Roadster is voiced slightly darker that the RK (many mention similarities between the RK and Tremoverb voicing), but this can easily be eq'd to being essentially the same. Again, I leave it to those with both RK and Roadster (and even Tremoverb) experience to speak to.
I'll leave it here for now for others to give their opinion, but I'm lurking. After a bit more conversation, if you still have some questions about how usable, and what impact, the features are that separate the RK from the Roadster, I'll be glad to hit on those.
Strat
Edit - Daisy was typing his response at the exact same time as me, so whatever he said, I didn't read. But probably agree with 100%.