As stated above, no one really knows what causes rosacea, though one of the possibilities is that the presence of a microbe under the skin causes the symptoms. Killing off the microbe seems to be the most helpful way to improve the appearance of skin and, if caught early enough, keep matters from getting worse. Only a handful of topical prescription treatments exist that can combat the microbe(s) responsible for rosacea. The success of these topical medications, when combined with an oral antibiotic, can be significant. Nevertheless, when you are considering an oral antibiotic you must take into account the risk of microbe resistance taking place after prolonged use (meaning that after period of time the antibiotic will no longer be effective). If that happens, that specific oral antibiotic will no longer be effective to help with other types of infections you may encounter, limiting your options if you get sick.
The most popular topical treatment is metronidazole, under the trade names MetroGel, MetroLotion, or MetroCream. It has been well studied and has shown impressive results. It is particularly effective when paired with an oral antibiotic such as doxycycline. Daily maintenance with topical metronidazole can absolutely decrease relapses and allow for longer intervals between flare-ups.
Another topical option is to use a prescription medication that combines benzoyl peroxide with erythromycin (an antibiotic), the same one that is more typically recommended for those with acne. There is some research showing it can be as or more effective than topical metronidazole. (Sources: Journal of the American Academy of Dermatology, January 2007, pages 107-115; Cutis, January 2007, pages 73-80; and Journal of Dermatology, August 2004, pages 610-617.)