Diedhiou is looking for a new club after being let go by Bristol City at the end of this season, upon the expiry of his contract.
The 28-year-old departs Ashton Gate having scored an impressive 51 goals in 169 games for the Robins, after joining from Angers in 2017.
At 6-foot-4, Diedhiou would add plenty of physical presence to Derby’s front-line, but plenty of goal threat, also.
The striker has hit double figures in his four seasons in English football, and clearly knows how to find the net in the Championship.
Derby were the lowest scorers in the Championship this season, and Rooney needs to bolster his attacking options going forward.