Rosones is a clever and playful slang word. It's a play on the word rosas (roses), which the singer's ex receives from her new, 'tame' boyfriend.
Rosones can mean large, showy roses, but here it carries a double meaning of something more intense and passionate, like scratches or hickies from a rough-and-tumble romance. The singer uses it to contrast his wild love with the boring, conventional flowers from his rival.
This song is one big, confident message to an ex. The singer sees a picture of her with her new boyfriend and is completely unimpressed. He says her smile looks forced, "Esa sonrisita se ve que es de a huevo" [That little smile looks forced], and that this new guy is too nice for her. He's blunt about it, claiming she's not an angel and actually likes it rough: "A ti, te enamora que te jalen por el pelo" [You fall in love when they pull you by the hair]. He's basically telling her that her new, tame relationship can't compare to the wild passion they had.
The whole song is an open invitation for her to call him when she gets bored. He tells her to "Manda un SOS si el vato ese / No te hace locuras como yo te hice mil veces" [Send an SOS if that guy / Doesn't do crazy things for you like I did a thousand times]. He contrasts the new guy's sweet gestures with his own over-the-top ones, saying, "Él te da rosas y yo rosones" [He gives you roses and I give you big, flashy ones]. He's so sure she still wants him, he just tells her to send the signal and he'll be there in ten minutes to "save" her from her boring new life.