As cause of rosaces is still unknown so the main goal of treatment is to keep the conditions under control. Have you found out which triggers your rosacea ? Make a list of things, (a sort of daily diary would be great) find which conditions make it worse, could be either some foods ( spicy foods) or eating habits, heat, cold, wind, stress, skin care products you are using, and your current exercise habit or anything that you might note.So the most important steps in prevention is to know which factor is making it worse, after you know the factor you can avoid it.
Does excess exercise makes it worse or sweating during exercise makes it worse, if its sweating try not to sweat by keeping your body temperature cool and when you know you are sweating and your rosasea will worsen you might get nervous and tends to get more sweat. So avoid stress.
So if gym means a lot for you and its worsening the rosacea, you can still reduce the excessive heat and sweating during your exercise by working out either in the early morning or late evening when the weather is cooler, Exercise frequently but for a short interval and keep the surrounding cool, use fans or open windows.Make yourself cool by drinking cool fluids.
yea you can use moisturizers for rosacea but remember even moisturizers tends to worsen rosacea in some people. So you should find it by yourself, which will suit you the most. Avoid using hot or cold water during face wash, just use lukewarm water.
There are many treatments options like topical metronidazone or clindamycin and laser therapy that might minimize the symptoms, you should be consulting the doctor for this.
But its important to know which environmental condition is actually worsening your symptoms.