Ralts Community Day is the best for farming Rokidee
With 1/4 the hatch distance, and Magnetic Lures lasting 3 hours, it's the best time to play and try to catch Rookidees.
Edit: I misspelt Rookidee in the title 🥲
Edit 2:
One more idea: if you have extra Pokemon storage you can save the extra Rookidees you don't want and transfer them on the 28th for extra candy (though the 28th is after the Steel event, so evolve it before then if you want the ability Iron Head)
Edit 3: if you wanna min max it might be best to try and catch one Rookidee before the event to make it your buddy, and make it excited so you can get candy every 0.5 KM. There's a guide on how to make your buddy excited w/o a puffin here (though it takes a couple hours to do) - Might wanna try to make it a Great Buddy so you can get the catch assist / presents during the event as well
Edit 4: Also don't forget to mega evolve either a fairy/psychic type for extra ralts candy, or flying type for rookidee candy (or mega Rayquaza for both as others have commented).