Rogers proved she could play on clay earlier this year when she reached the final of the Rio Open, but the unseeded American had never been past the third round at any major tournament in her career. Meanwhile, Begu had enjoyed the most consistent clay court season of anyone in the field, reaching the quarterfinals in Charleston and Madrid, and the semifinals in Rome.
Nevertheless, Rogers has been the Cinderella story of the tournament, taking out No.17 seed Karolina Pliskova, Volvo Car Open finalist Elena Vesnina and No.10 seed Petra Kvitova just to reach the second week. Playing on Court Suzaane Lenglen, she took it to her Romanian opposition, hititng 15 winners and nine fewer unforced errors than Begu, who only hit 12 winners in two sets.
"I think any player has to be ready to do well every week," she said in her post-match press conference. "We enter the tournaments with expectations, of course, to do well or work on things or, you know, with certain goals in mind.
"If you don't expect to do well, then maybe you shouldn't play, you know. I keep going back to trying to treat this as any other tournament, any other tennis match. Obviously the stakes are much higher and the players are much better.
"I'm just trying to stick with my routines and do what I have been doing all year."
Up a set and 4-2, Rogers briefly saw her lead under threat as the No.25 seed surged back to level the second.
"I won the first set and it was working. Okay, I missed a few, but still going for the right shots kind of thing. So just keep going after it I kept telling myself. It was working in the first, it's going to work again. So keep doing it."
Maintaining the course, a fifth break of serve in the tenth game proved decisive for the 23-year-old American, who clinched the biggest win of her career in one hour and 21 minutes.
"I really enjoyed playing on that court. It was a great experience.
"I think that's a very important point on backing up a big win. I guess I have done that pretty much this whole tournament, starting with the first round, because that was a huge upset for me and kind of set the tone for the last few matches I have played."
Setting up a quarterfinal encounter with No.4 seed Garbiñe Muguruza, Rogers becomes the first American not named Venus or Serena Williams to make it this far at the French Open since 2005 (Lindsay Davenport) and, at No.108 in the world, the lowest ranked player since 2012, when qualifier Yaroslava Shvedova won her way into the last eight, ranked No.142.
"I keep reminding myself to play one point at a time and that this is just another tennis match. But that's getting a little bit harder to do as the rounds get farther.
"But I'm very happy with the way I played, and I just hope to continue it."