If you take a look at the Almerimar Today website I have just published a brief story with a link a copy of an old winter bus timetable I scanned in some time ago. You will see that it looks like there are no direct buses to Roquetas unless things have changed recently.
The story also links to the El Ejido town hall website where they have a story in Spanish about summer night buses.
Sorry I don´t have any more recent info but at least this is a start.
John