As if Sasha turning Rosita's suicide mission into a solo trip wasn't shocking enough, The Walking Dead found a way to twist the start of this confrontation into another cliffhanger. Who found Rosita on The Walking Dead? The shadowy figure with the crossbow, who Rosita encountered at a distance while running away from Sasha's ambush in the final moments of the episode, is quite literally either a friend of foe.
The first candidate is Daryl, who has recently been reunited with his crossbow and may have left the Hilltop to go after Negan's two assassins. Towards the middle of the episode, Daryl confronted Jesus and Gregory, demanding to know where Sasha and Rosita had gone. If anyone was going to join their quest, it woud be him. As a former prisoner of Negan's, he knows what the Savior compound is like inside. He has made amends with Maggie and could be ready to take on Negan again. That's also, obviously, the preferable scenario, because it means that Rosita has an ally on the outside — and Sasha's sacrifice won't be in vain.
However, it's far more likely that Daryl's scene in Barrington House was a red herring and Rosita was stopped by Dwight, the Savior who also carries a crossbow. He wasn't with the group when Rosita was spying on them. It's the perfect fake out. Frankly, Dwight would be thrilled if he knew that there was an audience watching who thought he was Daryl. I don't know if you've noticed, but this dude is kind of obsessed with him.
That would mean that Rosita is in danger... most likely. There is, of course, a slight chance that Dwight will turn on Negan — but I wouldn't keep my hopes up. Rosita and Sasha made a rash decision, and those are rarely rewarded on The Walking Dead. This mysterious encounter is only the beginning.