It's not very hard to roll cast 35' with an FF75 and 5wt cortland peach WF (so nothing "optimised" for roll casting). The FF79, the rod specifically asked about, will do better - both because its action is better suited to roll casting and because it is longer. Both rods, being rated 5-6 wts, will be more comfortable (require less effort) for roll casting with the 6wt.
I can’t comment on the FF75, but I agree that the FF79 is a good roll caster, and better with a 6 than a 5; in fact that’s a reason I’ve gravitated to a 6 for my uses for it. I think when you’re at 7’6” or more in the mid line weights, pretty much any glass rod will to the job, some better than others of course.
And to Peters’s original post, I think a lot of the discussion about how different 6 foot rods roll cast is because of why they’re often chosen; when I take a rod that short, it’s because of stream cover. Even then streams vary, and some might require more sidearm casts under the rhododendrons, some more roll casting, some more aerial presentations, but roll casts are almost certainly part of the decision, and there are definitely differences in how those short rods will serve that function. But you get up past 7’ or so and a) most glass rods seem to fill the need well, or at least adequately, and b) conditions are rarely so tight as to require roll casting to be the primary factor in choosing that rod, or else I’ve taken a shorter rod. So at 8’, I pretty much don’t worry about it. That said, if you were to ask which of my 8’ 4-6 weight rods is the best roll caster, my response is, I don’t know. FWIW, the FF79 isn’t the automatic answer, but neither is it immediately placed at the bottom of the list - and neither is any of the other 5 or so rods in that length/weight range. They all do the job.