Leeds paid the big bucks to sign Piroe from Swansea this summer and he has already found the back of the net three times in six Championship appearances.
His goals against Ipswich and Millwall played key roles in getting Leeds two wins on the road already in the ongoing campaign.
Piroe will likely start against Hull at the MKM Stadium and Rosenior conceded that his record at Swansea previously speaks for itself and his finishing ability is a major threat in the Leeds armoury.
However, the Hull boss is certain that Leeds boss Daniel Farke is acutely aware of the attacking options his side will encounter on Wednesday night in East Yorkshire.
Rosenior told BBC Humberside Sport: “He is an outstanding player.
“He was outstanding for Swansea. You give him a chance, more often than not he can finish.
“We have played against them before.
“They have got threats but I am sure Daniel Farke will be looking at us and making them understand our threats too.”
Piroe scored 19 times in the Championship last season and seems to have carried his scoring boots from Swansea to Leeds.