As fate would have it...we are the same size...and a good size to be. 58 on the button. Reach will be right...I have a 110mm stem turned down...correct amount of post showing...not too much...not too little. Toupe is set just a hint aft of center in the rails. I could ride a 120mm stem...and probably will in the summer. Hey guys that seek Roubaixs aren't terribly flexible so you didn't even have to mention that.
You will really enjoy the riding position.
I just built mine up with Campy...you don't see a lot of Campy Roubaixs...or Tarmacs for that matter...and just got it out on the road for a 40 deg shake down run. Got a late start and did a quick 20 miles. This bike lives up to its reputation...very comfortable and fast. I ordered the frameset from Specialized. Robaix Pro...threaded BB....10r FACT carbon, hidden cable routing. Let me know if you have any questions about fit or specs. Below is pic of my bike...have red tires on order.
What I can tell you is the bike doesn't feel plush...but bumps are very muted. This is achieved with a stiff frame laterally with relaxed angles. The long wheelbase, pronounced fork rake and rear triangle geometry give the bike a good ride and yet the frame is stiff for energy transfer. The bike isn't nervous or quick handling...just goes where you point it. I wanted the bars close to my saddle level which is easy to achieve with this geometry even with our long legs. If I want a bit of drop, I can slam the stem to the steerer.
Hard to go wrong with a Roubaix for distance riding.