In the end can't say I can fully blame Roberto for this mess.
He exploded in 2015/16 as a good utility player in the squad as we were fucked by the transfer ban that season and injuries as our bench was weak and the signings of Arda and Vidal didn't work out as plan. perhaps one of the biggest gifts Lucho gave us during his time here.
The system we have clearly doesn't benefit him at RB, He's being asked to be that Jordi Alba on the right hand side despite lacking the pace and defensive ability. Asking him to cover that much ground especially with Messi in that false RW role with his current deficiencies is not a good idea at all especially considering his cover is Jelly legs Rakitic and a decaying Pique who was never the greatest 1v1 defender out there.
These problems will persist until Valverde finally realizes you can't play certain players together anymore. If you want Roberto to be the starting RB, you need to bring in a CB who is comfortable defending wide areas and 1v1s and an actual RW who can help Roberto out as well. Not this current setup we have now.