Bad times fella. How much time did you have left? Do you know how to force mate here? In future take a move to get your rook far away from the king so there's zero chance of doing that again. Then you can search your memory for a second for the way to win. Some decent tactics from you amongst some dubious play gg.
Or something similar. Oppose the King and force it back rank by rank. As you see even though it is forced win it takes a good 30-40 moves maybe more if the losing player is trying to flag you and drag it out as long as possible. You might need to play this at speed so get it absorbed or suffer again in the future!
I think there is nothing benefit for me to learn tactics or strategy because I however do such a big mistakes and blunders in my games. And even to learn how to make mate with Rook is useless, because I failure in a stress situation of game like in this one. How to avoid blunders and mistakes?