Night in Berlin

According to Deutsche Bahn Website the last train to Rostock leaves at 20:43, so you'll actually have to stay in Berlin over night. To find connections from Berlin to Rostock for the next day, check www.bahn.de. I think you can also get on the train at Potsdamer Platz, but not sure. Definitely at Hauptbahnhof.
To find connections from Schönefeld Airport to anywhere in Berlin, check www.bvg.de (the public transport website).
As to where to stay over night (and make the most of the couple of hours you have in Berlin) you'd have to tell a little more about what you like/want/prefer (Hotel <> Hostel, nightlife <> museum,...).

Thanks for your help! I'm travelling with my boss, who I can't imagine in a hostel, so I think we need a hotel, but my budget isn't huge, which I guess will make things difficult. I think we would just want to eat nearby, not really nightlife or anything. I was hoping that we might get a little bit of time in the morning to see something, so I feel like I have actually been to Berlin, even if its just a walk around the centre to get a feel of the place! Other than that, somewhere that will be easy to get to from the airport and easy to get to the station from. Sorry, that is probably not very useful, any ideas would be really helpful!
Thanks again!

Chloe

there's the "Etap" chain of budget hotels which you either love or hate (obviously, I love them) with one right in the centre of Berlin (Potsdamer Platz) and one close to Schoenefeld airport (and one on the outskirts of Rostock...).

Rental cars are rather cheap in Germany (rental car itself will cost you about the same as the train ticket for two people - add roughly 20 Euro for fuel) so this would be an option adding flexibility / mobility to your travel plans. I would not want to go all the way to Rostock the night of the arrival, though.

Try the Ostel - www.ostel.eu

It is close to Ostbahnhof, ideal when you come in late from Schoenefeld and need to take the train the next day.

The Ostel is a hostel and hotel. They have dorm as well as single and double rooms with ensuite bath. The best thing however is their unique GDR-style interior. If you want to get a feel what Berlin is all about even when you do nothing but sleep there, stay at the Ostel.