migraines cause dilation of some of the blood vessels in the head. there is also inflammation around some of these blood vessels also directly caused by the migraine. if this affects the blood vessels in the face the rosacea may become much more noticeable. migraine often causes patients to have a very pale face due to the nausea and feeling sick. rosacea would also be much more noticeable then as well. (you don't mention if you are male or female -- unfortunately some women have increased headaches as they near menopause which is co-incidentally when rosacea appears in women. )
at 56 i have had migraines since my teens. recently i have daily headaches and developed rosacea. are they related?