"Antique" encompasses approximately 100 years ago to 600 years ago (for glass beads) and to 1,000 years ago for other materials. The Roman Period was 2000+ years ago. So "antique Roman" is nonsensical. One would say "ancient Roman."

In the bead marketplace, there are not very many beads that would be rightly characterized as "Greek." There are some, of course. They are mostly not glass beads, apart from some very archaic types from early glass history. (These are well-discussed in the Proceedings of the Istanbul Bead Conference, 2007.)

Here's a dialogue that may help you understand time periods, and some basic ways to think about beads:

http://beadcollector.net/cgi-bin/anyboard.cgi?fvp=/openforum/&cmd=iYz&aK=49178&iZz=49178&gV=0&kQz=&aO=1&iWz=0

Good luck. Jamey