What is expected varies from parish to parish, as each priest is different. If you meet with the priest before or after Liturgy, it would be appropriate to ask for his blessing. If you speak with him when you go to venerate the Cross at the end of the Liturgy, then you would not ask his blessing, you would simply kiss the Cross, then his hand. But be careful about striking up a conversation during the veneration of the Cross, in my experience, most priests prefer that you engage them after services are over. I wouldn't sweat it though. You're not Orthodox. Most priests are understanding. If the priest is not understanding, well then don't be upset, chalk it up to an exercise in humility. You'll be fine. I've noticed some people think of ROCOR as the ultra-traditionalists of "canonical Orthodoxy", as a pharasaical sect, but in my own experience, ROCOR priests are almost always friendly, kind, and considerate.