There are lots of issues going on with your skin and scalp.I can understand your concerns.
To be sure that you have got Rosacea
or not you have to see a dermatologist
really,a picture of your face in a close up would be helpful but obviousely its not there so I can't comment on it further without seeing it.
Now regarding your question regarding Psoriasis
,it's very easy for a dermatologist to distinguish between Psoriasis and Seborrhoeic Dermatitis
by examine the scalp and obtaining the history from a patient.But sometimes it's not very easy for a dermatologist to do that like in case of SeboPsoriasis in which both conditions co exist so in that case we use to do a skin biopsy
on the patient which is then evaluated and a confirmation is made.
I hope you would understand my point.
All the best.