The England striker told manutd.com: "All the players are excited by their arrival. I know all about Owen Hargreaves from our time with England. You know what you're going to get with Owen - he's a top player and a good lad. I haven't seen too much of Nani and Anderson although I played against Anderson in a friendly once.
"Nani hasn't been able to train yet but I'm sure both of them will do really well for us."
Rooney admits United's current squad is the strongest he's seen at Old Trafford.
"Yes, definitely. There are more players and better quality players as well. There's a good mix of youth and experience which is great for the team. It's definitely the strongest squad I've been involved in."