K+R+R vs K+R Endgame

I wonder what is the strategy in an endgame with King+2 Rooks vs. King+Rook? What does the better side have to do? How can the worse side defend?

You just have to force the rook trade and after that K+R vs K is a win. There is nothing the side with the 1 rook can do against 2 rooks.

I thought of that. But is there a systematic approach for doing so?

it could be hard to win, especially in blitz

I can't think of a situation where putting your rooks on adjacent ranks or files and bullying your way forward with the rooks and king does not work. You can shield your king from side checks with a rook and when you reach the side of the board, trading a rook or mating should just work.

Just position your Rooks on opposite edges to do a 'hand-over-hand' mate, driving the King against the edge with checks. Your own King can take care of itself; a Rook canot perpetually check it, as you just walk towards it, so that he has to take distance again before he can resume checking. Then you can start checking him. If he interposes the Rook, you trade. If he gets on the same rank (file) as his King, to prevent you checking from that side, you check from the other side, and trade.

 If I shield my King with a rook, then the rook is also shielded by my king, so he cannot control the rest of the file (if I try to step ladder mate my opponent)

The strong side should not try to shield its King. Just approach the opponent Rook until he runs out of safe checks.