Carter- a bit too common and trendy. Plus, Carter Robert will slur to become Carterobert.
Graham- Short, manly, and classic... love it! Graham Robert is nice. I would not choose this if your surname is 1 syllable... it would be too choppy.
Emerson- It is a bit girly. What about Emrys, Whitman, Booker, or Walden?
Oliver- I know quite a few baby Olivers, it's incredibly common. Moreover, Oliver Robert will slur to become Oliverobert.
Wesley- Love Wesley, it's so romantic! It reminds me of the Princess Bride... Wesley Robert flows the best of all the choices.
So... 1. Wesley Robert 2. Graham Robert (as long as the last name is not 1 syllable)