If we sell Rooney and Jones (I hope so), next season as homegrown players we have: Johnstone, Smalling, Shaw, Carrick, Pogba, Young and Lingard, which means that we can have a squad of 24 players (not including Rashford). If Pereira returns (he will), it means that we can have 25 players in the squad. Jose has never used in his career, a squad this big, He uses 21-23 players (we have 21 players right now), so even in the following season when Carrick and Young will leave, we can still field 23 players which is fine. So, no extra homegrown players needed.
Also, why on Earth would we want to sell Rojo in order to get Keane? Rojo is a way better CB as of now. He was our best CB this season, and we have (statistically) the second best defense in the league. And this season, it wasn't because of De Gea.