He said the hospital, which employs 720 and has more than 200 doctors with privileges there, would continue its residency programs and nursing school.
Roxborough's current management team, including chief executive Robert G. Souaid, will remain, said Michael Henrici, the hospital's chief human resource officer.
In January, Prime was named one of the nation's 15 top health systems by Thomson Reuters, a list that included Jefferson Health and Geisinger Health Systems in Pennsylvania.
Prime, which had net income of $54.65 million on operating revenue of $830.62 million in the six months ended June 30, buys hospitals that are under financial duress, spokesman Edward Barrera said.
The most recent public financial data on Roxborough show that the hospital had an operating loss in fiscal 2010.
Solis had purchased Roxborough, along with Warminster Hospital, from Tenet Healthcare Corp. for $25.5 million in 2007. In 2003, Tenet had paid $23 million for the hospital, which was founded in 1890.
Prime has been an active bidder for distressed hospitals outside its home market of California. Most recently it appeared to be on track to buy Christ Hospital in Jersey City, N.J., but withdrew the offer after community leaders resisted the sale.
The company was also a bidder last year for hospitals in Hawaii and Rhode Island.
Joshua Nemzoff, a hospitals mergers and acquisitions specialist based in New Hope, said he investigated Prime as part of his work for an official handling the sale of the nonprofit Landmark Medical Systems Inc. in Woonsocket, R.I.
In California, Prime has faced allegations of Medicare billing fraud and has been in disputes with a major insurance company and a union.
"At first blush the press on them is not very good," Nemzoff said. "What really happened, when you get behind it, there's no substance to any of the accusations."
He added: "They are probably the most profitable health-care system I've ever seen. They are extremely well-run."
Contact staff writer Harold Brubaker at 215-854-4651 or firstname.lastname@example.org.