Roberts said he felt something pop behind his right knee as he was about to dive into second on a stolen base. Dr. John Wilckens will examine him in the morning.
"Just the bottom part of the hamstring, where he felt it," Showalter said following the Orioles' 6-3 win over the Tampa Bay Rays. "It's early. Their doctor looked at it. Dr. Wilckens will see him tomorrow.
"That's a quick turnaround. Not going to say he's going to be able to play tomorrow. We'll reassess it tomorrow and see where we are. He's in some discomfort."
The last inning was filled with strange twists, including Evan Longoria being called out after passing Ben Zobrist on a play later ruled as an RBI single and a putout for first baseman Chris Davis.
"If they hadn't called it, they would have had a heck of an argument, too," Showalter said. "We were all watching it. We saw the same thing the umpire did. I haven't seen the replays or whatever. You're going to get an argument either way. We were fortunate."
Asked if he's seen a runner called out in that manner in the past, Showalter replied, "Oh, yeah. You haven't been in the minor leagues much lately, have you? You can see how it happens. I'm surprised it doesn't happen more, as well as people run and as aggressive as they are at this level. We were lucky."
Starter Miguel Gonzalez was fortunate to avoid injury after being hit on the left shin by Yunel Escobar in the fifth inning.
"He told me it was just a glancing blow, but that ball didn't move too far after it hit him," Showalter said. "I don't know how that's much of a glancing blow, but he seemed fine. He's, as he would say, a tough hombre. That's a good outing, that's a good start for him."
Gonzalez stayed in the game after a few warmup tosses. He wasn't going to let a bruise on his shin end his afternoon.
"He wouldn't let anybody look at it," Showalter said.
Davis had 11 RBIs in the series, making him the first Oriole will 11 or more in a series of three games or fewer since Cal Ripken on May 28-29 in Seattle. Ripken drove in 11 runs in two games.
Davis broke two bats in one trip to the plate in the eighth.
"They broke Wonder Boy the last at-bat, so I don't know how he's going to do from here on out," Showalter said. "They got two of his bats. But he's got a couple more. Chris is in a good spot right now."
When the dust settled after the crazy ninth inning, the Orioles had won a game and a series against the Rays.
"It's always tough anywhere in the American League East," Showalter said. "It's one of the best teams we're going to play against. They're going to be around all season. This is just the start. There are some more battles along the way and we were fortunate this time. We'll see where we both are when we see each other again."