chalky
I’ve run them with 26mm Specialized Turbo Tubeless and currently have 25mm Schwalbe Pro One Tubeless on, and at 65 psi Front / 68 psi Rear measure up at around 28mm. The tyres run pretty much flush with the side of the rims.
I’ve done about 4000km on tubeless this year (mainly around Hampshire back roads, which are ‘variable’) and not had any issues running such low pressures. Was a bit surprised at where the pressures ended up, but I’m from a MTB background so don’t have any roadie baggage as to how one ‘should’ set up their bike. That’s just where they settled after a bit of trialing.
FYI – some of the Hunt rims have very similar rim diameters, and they advocate running 25mm tyres on 21mm internal rims. It was that corroboration plus other bits of reading which gave me a bit of confidence in the LB rims (or similar) would match well with the Roubaix.