I think many of our cities are going to be capped by happiness soon so unhealthiness will not be an issue in most of our cities. Heck, it'll probably curb growth so that it'll save city maintenance overall. I would go ahead and hook-up oil. If we can conquer some of Roos's cities earlier, we can set them to wealth/research and have them break even before the end of the game.
I think roosy is best left for the end since it will cost more to take him now than any benefit we would get from it.
shyuhe I copied any earlier post about the war with Roosy decision below. I think one of the reasons we don't want a war with Roosy is because of our low happiness caps. WW with him will be significant even with tanks. The
from oil is basically equal to 4 sushi resources which we are paying at least 2-3 gold per city for in maintenance. If we do hook up up oil why would we want it hooked up more than 1 or 2 turns (since we could build 15 tanks in 15 cities over those 2 turns) would save us lots of food that we are paying for anyways. Why not take the food if we can? Why throw it away?
If we attack Roosy before the spaceship
1) we lose trade routes with him (which isn't that significant)
2) we lose trades with him (for some reason he isn't canceling the seafood trades)
3) we lose the benefits of the builds that we would do instead of a modern military. We can't take roosy's rifles/cavalry/cannons with our current army without a lot of losses. (we need wealth builds now along with observatories and other useful buildings in most of our cities)
4) we suffer more war weariness that we can't easily deal with, without taking a significant research rate hit.
5) it would not be wise to gift him any more techs (if he gets artillery we definitely want to wait to attack him for example--or it just becomes even more expensive to attack him)
6) each addition military units costs us at least 3 gold per turn in addition to its actual cost. Just 1 tank is 180 gold up front and then 3 gold per turn that could otherwise keep our research going...
7) We do get the production of his cities that we capture. But realistically we start the war in 10 turns? Then revolt for 6-10 turns which gives us 10 productive turns?
editted:
If we attack after the spaceship launch
1) We only have 10 turns, but every city can be devoted to his destruction without slowing down our victory date.
2) We might be able to steal artillery from him (by gifting him some techs) (edit: less likely now, but still a possibility
edit: 3) leaves open the possibility of gifting him ecology if he remains our friend so he cleans up some fallout for us.