Sun exposure is usually the most common trigger for a rosacea outbreak. Solar radiation induces inflammation of blood vessels and oxidative damage. Sun protection must be used throughout the year, not only in summer, and both outdoors and indoors, where blue light is present. Always wear an SPF of 50 or higher and keep your skin protected from the sun.
Everybody's skin is different. Always consult your skincare professional when introducing something new to your routine.