Not letting Kershaw finish. Letting Alexander just swim out there until he gave up 4 before bringing in Baez. Roberts is not the only problem. The GM needs to go too for being unable to shore up the pitching.
This is just patently absurd. Kershaw, who was at 110 pitches after 8 innings, who has already been on the DL twice this year, who has had recurrence of back issues for three consecutive seasons that has sidelined him for extended periods of time each of those seasons, who has seen a substantial downtick in his velocity this season, who is on the wrong side of 30, who has not surpassed 112 pitches in any start this season, who has not pitched into the 9th inning since April of 2017, should not only have gone out for the 9th inning, but been allowed to finish? That's laughable.
And stating that Roberts failed by "letting Alexander just swim out there" as if there was some knight in shining armor that could have come in and saved the day. Again, Alexander has, by all measures, been the most reliable member of the bullpen (see, e.g,
Scott Alexander is one of baseball’s biggest outliers) since he was recalled from AAA (and no, Ferguson does not count because he has not yet been pitching in high leverage situations, though he clearly has pitched quite well out of the bullpen) . Whether you like them or not, Cingrani and Fields proved themselves to be quality and reliable members of the bullpen, but they are on the disabled list and unavailable to pitch for Roberts at the moment.
And in what world does it make sense to get rid of a GM (not sure if you're referring to Zaidi or Friedman, but we'll just consider them as one for the purposes of your argument) who has constructed a team that has won three consecutive NL West titles, and gone to the NLCS and lost to the eventual champion in 2016, and gone to game 7 of the World Series in 2017. Yes, winning would be nice. But it's f***ing difficult. Only one team wins every year. The odds that your team is the team that wins are miniscule.
Not to mention the Dodgers are perfectly in contention to win the division again this year, despite losing their All-Star shortstop early in the season, despite missing their leader and star third baseman for the first month-plus of the season (not to mention it has taken Turner a while to round into form, the attempt at which was unfortunately interrupted by another DL stay), despite losing various members of their starting rotation (including their nominal ace) for differing amounts of time, and despite losing important members of their bullpen for different periods of time (Cingrani, Fields, Jansen, Koehler). Yes, they traded for Machado. That doesn't make up for the few months they were without an All-Star-level player at short. There's also the fact that Machado has struggled extensively the last several weeks.
You say the GM should be fired for not shoring up "pitching," without specifying starting rotation or bullpen. I'll assume you mean bullpen because the starting rotation, despite its constant shuffle (and extended loss of its admittedly diminished ace), is still 6th in all of MLB in WAR. Don't like sabermetric stats? Fine, the Dodgers starting rotation has the third best ERA in all of MLB. So, surely you can't be whining about them.
As it pertains to the bullpen, did they let Morrow go to the Cubs and not adequately replace him? Yes. There's an argument to be made whether you should be spending $11 million against the luxury tax threshold on a non-closing reliever, but let's assume letting Morrow go was a mistake notwithstanding financial implications. This front office (along with Honeycutt) has a track record of turning broken down, has-been pitchers into excellent relievers (see, e.g., Blanton, Morrow, Cingrani). They attempted another such project this year with the signing of Tom Koehler, who had a recent track record of strong performances in the bullpen (
Tom Koehler ready for whatever role the Dodgers need ;
The Dodgers’ Attempt to Beat the Market | FanGraphs Baseball). That signing undoubtedly has not worked out, but not for lack of trying.
Predicting reliever success from one year to the next is an exercise in futility, save for very few relievers. Relief pitchers, by nature, are a volatile bunch. (
Consistent bullpens and unicorns ;
David Robertson and the Dangers of Reliever Volatility | FanGraphs Baseball). To look back now in hindsight to say they should be fired for not shoring up a volatile position is the epitome of pettiness, particularly when the concern is so acute entirely due to Jansen's absence. If Jansen was not out and was able to save the last couple disasters, any statement now that you'd be saying the same thing strains credulity.