Is this for TF2? Since it looks like you're up for learning how to do it, here's some steps you can follow:
Add a command listener to the "voicemenu" command and detect the "MEDIC!" call. You can use this snippet (ported to new syntax, ideally). Make sure it works by displaying some messages with PrintToChat or PrintToServer before moving on.
Determine the position to spawn your rocket (likely with GetClientEyePosition and GetClientEyeAngles), then spawn your rocket. This snippet should be fine, though it's also in old syntax.
Set up a cooldown. Create a float array for your players (size MAXPLAYERS + 1), then when you need to update your cooldown, set it to GetGameTime() + your_cooldown_amount. You can check if the cooldown has passed if GetGameTime() is larger than the array entry. Don't forget to zero out the time in an OnClientPutInServer() forward.
Thank you! I shall give this a shot. I am a little unsure of new syntax vs old, but im sure some trial and error will solve that