How do you treat and prevent Acne Rosacea?

[Adel]

My acne is moderate. I tend to break out on my face, chest back and arms. Almost all over my upper body, but my limbs. However, I have these different looking rashes on my neck and under arms, which the doctor has diagnosed as rosacea, which I thought was odd, because I am black, but with lighter skin. However, my concern is that perhaps all the acne I have ever had is actually rosacea and not vulgaris (the more typical acne). My face tends to be darker than my body and has a redder undertone than usual. I just don't know what to do, cause it seems to be spreading.