The Roswell TV series, which started out based on the Roswell High books by Melinda Metz, ran for 3 seasons from October 6, 1999 until the last episode aired on May 14, 2002.
There have been three seasons of Roswell. The first season debuted in October 1999 on The WB. The second season debuted in 2000 and the third debuted in 2001 and the series was moved the UPN for the third and final season.
There are three full seasons of Roswell, but many fans want more to come. Critics also agree Roswell could go for another four or possibly five seasons and I agree.