Naming and shaming is not allowed, so you should remove the name of your opponent. If you had enough time though, i don't get it. Rook and king versus rook and king is one of the easiest endgames to premove.
flagging

Yes, premoving should be the answer to such situations when playing online. OTB you can claim the draw as soon as you have less than two minutes without any increment remaining, if the arbiter agrees (which would be almost sure in this case).

Remember you must claim the draw like in OTB after the 50 moves without progress (capture or pawn move), it isn't automatical on this site.

I occasionally have an opponent who will try to run me out of time rather than accept a draw. I just make aimless moves until I have less than 10 seconds on my clock, and claim a draw (It's easier than counting moves or looking for three-fold repetition). Most of the time, we have made more than 50 moves. Periodically, I lose on time. It's annoying, but no big deal.

Hi Everyone,
I just played a 10 minutes game where I was blatantly flagged (by S_Czyrnek).
We reached a position with King+Rook versus King+Rook, completely drawn, but the guy declined draw, and played for forty moves or so, until my flag fell. (I have been shorter on time all through.) I don't know if it is legal, but I think it is certainly unethical.
What do you guys think?
BTW, if there are 50 moves without pawn move, does chess.com detects it and decides that it is a draw. This could have helped to some extent. Also, blacklisting flaggers could help.
Thanks for your feedback,
Michael
It's within rules, especially if you reached an equal position with less time. Next time you will know to move 50 times quickly or pin his rook to the king.

Well, you shouldn't have lost on time on such a simple endgame position, it is really easy to draw, its your fault.
I won many bullet and blitz games that way. Does that make me a cheater? I mean of course I will not resign in a game 1+0 where I am rook down while having 35 seconds on clock and my opponent has 5. I have every right to play until he runs out of time.

Time management is part of the game, and flagging your opponent is entirely legal. In fact, in fast time controls, it's a very common - and legitimate - strategy to try to flag your opponent rather than beat them on the board, by playing aggressive moves that will force them to burn time figuring out how to defend. If flagging was considered bad, why do we have clocks?
As to your question on the 50-move draw, chess.com implements the official rules: either side may claim a draw after 50 moves with no progress, and the draw is enforced after 75 moves with no progress.
See the laws of chess here: http://www.fide.com/component/handbook/?id=208&view=article
Note especially 9.3.2 and 9.6.2.
The laws are similar for three-fold repetition: either player can claim a draw after three repetitions, and the draw is enforced after five repetitions.

If you out-play your opponent but lose on time, that shows he managed his time better than you and thus earned his win.
You have two resources:
1. Time
2. The position on the board (material, positional factors, etc.).
You need to balance both of them. If you focus on the second and neglect the first, you have neglected half of the game and will therefore risk losing.

I occasionally have an opponent who will try to run me out of time rather than accept a draw. I just make aimless moves until I have less than 10 seconds on my clock, and claim a draw (It's easier than counting moves or looking for three-fold repetition). Most of the time, we have made more than 50 moves. Periodically, I lose on time. It's annoying, but no big deal.
How do you claim draws here in chess.com? I´ve noticed the system doesn´t gives draws automatically in threefold repetition positions, so, if you are up on time you only have to make the same move eternally.

To claim a draw, you hit the Offer Draw button.
Chess.com follows the FIDE rules for draws on three-fold repetition and 50 moves with no progress: either side can claim a draw after three repetitions or 50 moves with no progress, but the draw is not enforced until five repetitions or 75 moves with no progress.
If you have reached three repetitions or 50 moves with no progress, hit the Offer Draw button, and you will be awarded a draw. Or play until five repetitions or 75 moves with no progress, and a draw will be enforced.
Hi Everyone,
I just played a 10 minutes game where I was blatantly flagged (by [name removed - MOD]).
We reached a position with King+Rook versus King+Rook, completely drawn, but the guy declined draw, and played for forty moves or so, until my flag fell. (I have been shorter on time all through.) I don't know if it is legal, but I think it is certainly unethical.
What do you guys think?
BTW, if there are 50 moves without pawn move, does chess.com detects it and decides that it is a draw. This could have helped to some extent. Also, blacklisting flaggers could help.
Thanks for your feedback,
Michael