I think it would be actually more fun to say who should have gotten an Oscar and for what film should they have received it for.
So for Roger Deakins, of the films he has been nominated for:
1995 - Legends of the Fall won, Deakins was nominated for The Shawshank Redemption, but Three Colors: Red was also nominated and should've been the actual winner.
1996 - The English Patient won best cinematography. It deserved it, even more so than Deakins' work on Fargo.
1997 - Titanic won this year. I believe it's a deserving winner, but so are many of the competition which includes Amistad, L.A. Confidential, and Deakins' Kundun. I am split on this year. Any one of those could've won and I would've been happy. No clear-cut frontrunner here, so I wouldn't give him it.
2000 - Crouching Tiger, Hidden Dragon won. Iit's clearly better than Deakins' work on O Brother, Where Are Thou?
2001 - Fellowship of the Ring won. Deserving winner, though I have yet to see The Man Who Wasn't There, my only major blindspot of the Coens' work. I abstain.
2007 - There Will Be Blood won and it's extremely deserving, even though No Country for Old Men AND The Assassination of Jesse James by the Coward Robert Ford are career-best work.
2010 - Inception won. While I think True Grit is more deserving, I also think equally the same for Black Swan and The Social Network, so I can't say he's the frontrunner here either.
2012 - Life of Pi won. While I love its work, it's mostly special effects based so it feels like more of a cheat than usual. I don't feel much for the other films nominated here, so I would give Deakins' work on Skyfall here an easy win.
2013 - Gravity won. Deakins' work on Prisoners is seriously overrated, so no.
2014 - Birdman won. Undeserving winner, but I never saw Unbroken, so I abstain.
2015 - The Revenant won. While I love Deakins' work on Sicario, Carol is also a very worthy winner, so I can't say he is the clear cut best here either.
Out of all his other work, Barton Fink, The Hudsucker Proxy, The Village, and A Serious Man all deserved Oscar nominations, but I wouldn't give any one of those wins in their own respective years.