Due to the quality of rugby and coaching, welsh players would 100% be better off in France or the premiership.
Debatable. Plenty if players moved and went backwards. Even Roberts himself played by far his best rugby when at Cardiff. North another who gradually got worse and worse at Northampton. Jekins, Lydiate, Webb, JD2, probably more I'm missing.
Biggar has probably improved, but otherwise probably gotta go back to were probably Stephen Jones and Gareth Thomas, and it's not as if they were poor players before leaving.
The quality of Pro xx / URC is dragged down by the Welsh regions, the Irish provinces consistently offer the best competition in Europe.
The regions need to improve, that goes without saying. There's quality and lots of potential there, but the coaching is sub standard and player pool thin in certain positions, especially up front. The 60 cap rule has done a lot to strengthen the regions, and long may it continue.
Otherwise the regions probably need better coaches (Ryan at Dragons show the improvements that can be made by good coaching), and more funding to source a couple of top notch foreign imports in key positions. That's desperately missing at the regions atm imo. Most top sides have one or two, even the likes of Leinster at their best had Elsom etc. Regions used to have some - Rush, Molitika, ***o, Blair, Hollah, Tiatia, Marshall, Collins, Bowe, King etc. They make a huge difference, pushing standards, and are often available all season.
Home grown talent is obviously still key, but I don't think the regions can be successful on home grown talent alone. The current imports at the regions are either journeymen, or second rate/inconsistent.