I land in Berlin at 5:45 PM and need to get to Rostock. I believe there is a train from the BER airport to Rostock.
What is a good enough time to get out of the flight, grab my luggage & head to the railway station?

Any thoughts from anyone who has used the train will be great. Thank you!

Have you had a look at the Deutsche Bahn website? You can do searches and mock bookings (i.e. just don't pay when you get to the final screens). I see a direct train, IC 2172, leaving Berlin Brandenburg Airport at 19:04 and getting into Rostock Hbf at 21:50. I don't think you can make earlier trains and later ones all require changes. Plus I don't know what day of the week you are travelling; Sunday timetables are a bit different. I selected a Wed just to have a baseline.

I would think it would take you a good hour to get out of the airport so I could be happy with a 7:00 train. But from that point I would pretty much seek out a hotel when you get to Rostock rather than try to continue on to a cruise ship (my assumption about what you are doing there so late at night). I don't know whether there will be taxis waiting at that hour of the night. Perhaps you could look at booking a taxi to meet you?

Lavandula