Meh, the rotation has depth but it's still obviously a weakness since it lacks quality. You have one elite pitcher in Ryu and then a million question marks. Robbie Ray projects well and will likely be much better than last season, but with his command variance that's still a decent number 2 at best, nothing compared to teams like the Dodgers, Padres, Mets, Yankees if healthy. Then after Ray is where you have a bunch of guys who may or may not suck.
On the whole, it's probably reasonably likely that one of Matz, Roark, Stripling, Pearson will be good, but unlikely all of them are. And because they're pitchers, even the good ones are going to miss time, which is where the depth comes into play. So then you're stuck with having a dozen #5 type quality starters following a great pitcher and a good one, and Ryu has injury concerns himself so if he misses a couple of weeks throughout the season then the rotation looks brutal.