Material advantage in a closed position

I had an interesting game which, unfortunately, was abandoned by my opponent. 

After he left, I tried to figure what I would do if the game went on. I didn't manage to find a way to win.

I'd like to have some help analyzing the reached position.

As you can see, I have a material advantage - but I can't find any way to open the game and bring my pieces into the game.

Is it winnable?

What would you do?

Yeah, rook(s) vs knight(s) with many pawns on the board, if there are no or few open files then the rooks aren't too effective.

You said you can't find a way, but a5-a4 opens a file right away, so there's one way.

The downside to opening too much (not that you can force it) is that your pieces aren't very organized right now, and your king isn't so safe when white still has two rooks.

But yeah, push down the a file, weaken b4, trade some heavies, and black is has a winning endgame.  I suppose white will try to use the kingside/center.  Your king is loose and d6 might be targeted.

a5 was the first thing that came to my mind, but then ...a4 and the position remains closed.

Edit:

Oh god, forgot en passant.

Alright then. But let's be hypothetical - what if the position is the same + my pawn is on a4 and the black pawn is on a5. 

Is it winnable?

In that case I think it's a draw if white wants it (I'm guessing he does).  No files so your heavies don't amount to much.

Maybe sac the Exchange for a pawn to open up the position, and then try to break through? However, I don't think that will help much...

I think 1. g5, Nf3 (Ng6 Rg8 would trap him) 2. Re7

and after that (white cannot prevent it, nor create any counterplay) Rb8 and Rbe8 and than sac the exchange gives you an easily won position, also the a5-a4 idea should be enough (:

-edit: if he doubles rooks, you can sac anyway, and if dxe7 you can finally bring your queen in the game via d8 and start creating play on the kingside

The knight on e6 is worth more than a rook anyway so it's not even a real sacrifice.

Your position is chaotic, no doubt about that. You have very little space to move. Therefore, your main idea should be to get your King out of the way to give your other pieces room to breathe.

1...Kc8 opening up the row for your other Rook is a great start.

I would also consider Qa5 threatening the a2 pawn but with a real threat of placing the Queen on a3 to give yourself more room. It will also lock up his a1 Rook for awhile as your b4 pawn is very close to dangerous.

What I would do:

1...Kc8 2. Nxg6 Rf7 This threatens to fork the two Knights but more importantly opens up your position considerably. From there you have the choice of either Qa4 or Qa5 or Qb7 or fork his two Knights right away to force a move and gain time and begin moving your Queen down into open files.

Note: I didn't go through this position thoroughly. This is just the stuff that jumped out at me.