You've also got quite a choke point to navigate to get into the Black Sea. Sure you've got allied control of that, but just a couple of subs lurking at the eastern end, plus a determined sea mining effort would utterly scuttle any attempts to force your way in. Add to that the small issue of not actually controlling the Mediterranean end (Greece and Italy are very likely to have something to say about that little detail) and trying to send a decent sized fleet into the Black Sea becomes more trouble than it's worth. Even a single surface combatant is very unlikely to have much fun (and without supporting vessels will soon be on the bottom anyway).
A sub
might get through, but again, you've got active PACT naval defence forces watching for something just like that.
As for the Romanians, well, they're much more a defensive force with very limited offensive capability. It's highly likely they'd be quickly eliminated but not before giving the Soviets a bloody nose. Interesting to note that they only had one Kilo class sub delivered in 1986.
http://www.country-data.com/cgi-bin/query/r-11302.html