Larsson will leave United after the FA Cup tie at Middlesbrough today.
Rooney told The Sun: “Henrik has been absolutely brilliant. His workrate is unbelievable.
“The other week at Tottenham I was standing there and saw him racing back to defend. You think ‘You’re 35, how are you still doing that?’
“But he’s in great shape, his movement up front’s brilliant and we’ve done well when we’ve played together.”