Issue moving database between servers (cannot find .frm file even though it's there)
PROBLEM
You have a file permission issue.
The INFORMATION_SCHEMA database will not notice when doing just show tables; because it will scan for the .frm's existence. It's when the storage engine attempts to access the physical files (.MYD and .MYI') that mysqld will complain. All physical files of any table must have mysqlas its owner. When the error saysCan't find file: './roster/users.frm' (errno: 13)`, it really means it cannot find the table's physical files with proper file permissions.
SOLUTION
Change the owner of the roster folder and its contents to mysql.
GIVE IT A TRY !!!