My idea is that we can still play e4 now and meet Rac8 with Re1. Then after he plays c4 we can play dxc4 (or even d4) and we still have our pawn on e4 sufficiently defended. If you don't like the idea of moving our rook again we can play b3 after Rac8 instead of Re1
You've sold me on it.
15. e4 for me too, please.
Here is a recap including my vote:
15. e4 6 votes (boolberry, ErisDiscordia, gotmilk_, dre1982, Foxpup, abacus)
15. Bc7 2 votes (Febo, jjacob)
15. Ng5 1 vote (bitcoinboy12)
15. Ra3 1 vote (Timelord2067)
15. Rac1 1 vote (neochiny)
(Edit: I hope it's right, but I see there is some differences from the graph Taras has posted while I was writing this)
Rac1 plz... since e4 is not good because our d3 pawn will be weak in the end. like the a5 pawn...
and Bc7 is just a useless move since unless you guys want to exchange it.
Our d3 pawn is probably a dead man walking already, waiting for his own sacrifice to capture the black c-pawn when he moves.

I would say 15 Bc7.
We drive away the Rook and we can always bring our bishop back (if it is attacked).
The problem here is that we'll probably drive the Rook in a still favorable position, i.e. on c1. In this case we have to come back with the Bishop, with very few advantages for us. Maybe we could look again at Bc7 once the d file is open (if our Rook is still on d1).