The ROSE Online Servers undergo weekly server maintenance unless otherwise specified. The weekly server maintenance generally occurs on Wednesday or Thursday from 2:00PM - 5:00PM PST/PDT.
Any emergency maintenance should be announced ahead of time and notices can be found on the WarpPortal Forums.
The game servers are unable to be accessed until maintenance has been completed. Once maintenance is completed, you should be able to log in normally.
Make sure to log out when server announcements begin in order to avoid any potential problems.