Friendly units will often say "Roger WILCO" in response to a command from a player.
In the US Army, it is never correct to say "Roger WILCO", as WILCO ("I understand your transmission and will comply") contains the meaning of Roger ("I understand your transmission") within it. Radio operators are anal about proper procedure, though granted, everyone else is lazier about it. In my 4 years as a radio operator, I never heard anyone say "Roger WILCO" over the radio, and anyone who did would have been mercilessly mocked for doing so.
Minor issue, but it's like nails on chalkboards for those of us who know better.