I have rosacea...what is a good diet to control rosacea from spreading?

None!: Rosacea is not a disease that "spreads" or is communicable from or to others. It is a genetic skin condition that can be treated with oral and topical medications, the vascularity treated by laser to reduce redness, and the skin thickening reduced by laser resurfacing if needed--but rosacea is not "cured" or eliminated. Some foods can stimulate redness (like alcohol), but won't cause "spread.".

Bland food: Rosacea is tough to control. You have to avoid all triggers: extreme cold or extreme heat, any yeast-type drinks like wine or beer, extremely spicy foods. Basically avoid anything that will make your face flush. It's the flushing that leads to chronic blood vessel formation. I have rosacea myself so i know firsthand.