Quemarroba is a thrilling Spanish word. The phrase "a quemarropa" literally translates to "at the burning of the clothes", referring to firing a gun so close that the gunpowder flash would singe the victim's clothes.
Figuratively, it means "point-blank" or "directly and without warning". In the song, Romeo Santos sings "Me lancé a quemarropa" (I threw myself at her point-blank) to describe how he impulsively and vulnerably dove into the relationship, making him an easy target for his expert rival in the game of love.
Have you ever felt like you were playing a game of love and just got completely outplayed? That's exactly what Romeo Santos is singing about in "La Diabla". He tells the story of betting his feelings on a woman who he sees as a master strategist, a "diabla" [she-devil]. He admits he was foolish, comparing himself to the famously idealistic Don Quixote, and that he threw himself into the romance without thinking: "Me lancé a quemarropa y ella me venció" [I threw myself at her point-blank and she defeated me].
He sees her as a cold, calculating player whose "fichas y barajas no les fallan" [chips and cards don't fail her] and who has no compassion. But here's the twist: even after losing so badly, he's ready for more. He says if she ever came back, he would challenge her to a rematch, knowing full well he would "vuelvo y pierdo el corazón" [lose my heart again]. It's a classic bachata story of being drawn to someone who is totally wrong for you, and being willing to get your heart broken all over again.