The 30-year-old joined Rovers in a January loan deal after failing to impress for the Black Cats this season and came up with his new side's third goal in the victory which sees the Lancashire club move eight points clear of the Championship relegation zone.
Lambert said: "Danny Graham has scored at every level and it's funny because even when I was with Norwich, he was scoring goals with Swansea in the Championship.
"I always liked the way he played the game and there's always a hunger with him. You see his work-rate tonight, everything he gave us.
"If there's one guy I'm absolutely delighted for to score a goal, it's him because he's a top guy, top pro and honestly if we can keep him fit, he will be a very good signing for us."