The Protagonist Only Thinks About Falling In Love

I transmigrated into a novel as an extra named Rosetta, a side character destined to be killed by the male lead. The problem? The original male lead, who was supposed to be a cold, ruthless warrior focused on saving the world, is completely obsessed with romance! Instead of following the main plot, training, or fighting the demon king's forces, he spends all his time trying to flirt and fall in love with me. Now, I have to somehow push this love-struck protagonist back on track to save the world while desperately trying to avoid my own bad ending.