Nearly two years after giving up her actors union card, Patti LuPone, 74, will come back to Broadway this fall, The Post has learned. And, in typical LuPone fashion, her return won’t be low-key. The three-time Tony Award winner will star opposite none other than Mia Farrow, 79, in Jen Silverman’s play “The Roommate.” The production, directed by Jack O’Brien (“Shucked”), will begin previews at the Booth Theatre on 45th Street in late August and then open in mid-September.