Yes, during the Dominion war.
In the new timeline, possibly in the future, but for now to be determined.
In the new timeline not a chance in hell, a Romulan destroyed one of the fonding members of the Federation, and how many people are going to believe that he was from an alternate future timeline? the new universe might have the Klingons join the Federation before they ever side with the Romulans.
Nero was a renegade, with no connection to the 23rd century Romulan government (which the Federation is now aware of). He might not even have been born yet then for all we know. The 23rd century Romulan government (which the Federation has more knowledge of in the new timeline) could easily deny any knowledge of, or connection with, Nero. It is possible that, ironically, his actions could end up bringing the Federation and the Romulans of the 23rd century closer together. It would be entirely consistent with the nature of the Federation for them to reach out to the Romulans and warn them about Hobus, a problem they both now have 130 years to figure out how to solve. The next movie will supposedly deal with the aftermath of Vulcan's destruction. Could that aftermath involve diplomatic dialogue between the Federation and the Romulans, regarding both how to neutralize Hobus and how to help the Vulcans (although the 23rd century Romulans could legitimately claim that since they had no connection with Nero, they shouldn't necessarily be expected to bear total responsibility for his actions)? It's entirely possible.
"Captain, what are you doing?" "Showing them compassion, it may be the only way to earn peace with Romulus. It's logic, Spock, I thought you liked that."
question to the last post:
lets say that you, living in USA, have friends in Afganistian, you see 19 Afgan's fly jets into New York City killing 3,000 people, the government of Afganistian said they had no connection to this event...oh wait that is what took place in 2001, the US = Federation; the Afganistian government = Romulans 23rd cent new timeline, Nero = 19 Afganistian terrorists,
the US went to war with Afganistian due to the loss of 3,000 people, what would Earth due if an alien killed 6 billion people?
But to the last- The 9/11 Hijackers were not Afghanis; They were from Saudia Arabia, Yemen, and other Arab states. They trained and had safe shelter in Afghanistan with Taliban allies.
Back to Star Trek..with the loss of a major Federation world, and the loss of the taskforce sent to Vulcan..it would not be logical to declare war on Romulus due to the actions of a rogue Romulan from the future.
So, it's still an interesting analogy.
On a non-canon site called USS Miranda Wiki, the entire Romulan Star Empire is merged with the Federation in a 2387 alternate-reality map of the Alpha and Beta Quadrants. Also, according to the wiki, Romulus and Remus joined the Federation in 2325 (again, alternate reality). Despite some inconsistencies on the map that contradict statements in the franchise and on Memory Alpha, it's still an interesting thing to look at. Here's a link: