you need to go age 3 as fast as possible then use it once you hit age 3.
I only use it once when I reach age 3, you don't need to use it again if you set your economic correctly and it gives enough resources to do.
as for coop, I don't know if both need to use it I only played it once.
Since you easy (with good gear) can Solo Myrtoan Sea if using consumables both never need to use RoE, the other one can be with you in launch and go to lunch until you're done (of course with low score then). But if both want good score it's likelly both need to use RoE, it puts ju silly much ahead in the game when triggered. Not sure though if one can get good score even without, but to me it seems hard to beat 3M+ without. Not tried to many times yet though.
Well i have figured out a bit.
Got 3.7m points at least on solo.
I have used:
Villager / Elephants / Resources of the Empire. One time each used and 3.7m is okay for me... Hf Gl all
To add to this resource, found a video of coop getting 3.6mil score, no consumables, using ship strategy, so might not get you to top, but good into to getting higher scores