I also loved Roswell! I watched that entire show. It's another one that I should get on DVD. I could watch it again...I'm just going to have to get Netflix again, ROFL.
The Event is current. It's an NBC program that just started this season. It's just ten episodes in. You can watch here:
http://www.nbc.com/the-event/video/categories/season-1/1243881/
I'm two episodes behind.
Extra terrestrial beings who look just like humans & are very similar genetically. US Government has been keeping them secret for decades. Even the US Presidents were kept out of the loop. A new pres becomes aware & the situation changed drastically. The ETB's want to go home. Not your typical alien show.
Nikita is on the CW.
http://www.cwtv.com/shows/nikita/about
It's also in the first season. I've got a lot of hope for this one. It's got a good storyline/theme & plenty of eye candy of both genders. The eye candy alone should help it keep viewers, I'd think.
Secret "Division" that carries out assassinations. Nikita is a member of the "Division" who has gone rogue and is now targeting Division itself.
Jericho only ran for a couple of seasons (and the second was short).
http://en.wikipedia.org/wiki/Jericho_(TV_series)
SEason 2 is still up on CBS.
Nuclear attacks on 23 US cities...show centers on the folks in one small Kansas town, Jericho.
Jeremiah ran for a couple of years back around 2002. Starred Luke Perry & Malcom Jamal Warner. Another end of the world -- or close to it -- scenario. This time, most adults were wiped out by a deadly virus leaving only children behind, many of whom did not survive the chaos. Again, this just had a couple of seasons.
http://en.wikipedia.org/wiki/Jeremiah_(TV_series)