A forum post at GameFAQ:s indicates that you can use C&C:RA in 2-player skirmish mode, provided you have the right hardware.
Quote from GameFAQ:
If you're playing on the original playstation (The grey brick model, not the PS1), then you can utilise the 2 Red Alert games for linkup mode - basically a 2 player skirmish. Command & Conquer lacked a linkup mode as well as a skirmish mode. Such a setup requires 2 playstations, 2 TV sets, a linkup cable (This will be the hardest thing to get now, by far). As each game comes with 2 discs, you'll only require 1 copy of the game. The PS2 and later consoles are unable to utilise the linkup feature due to different hardware.