I was only able to find information and job openings for two opportunities instead of three. However there is more than one job opening for one of the links i will provide so bare with me please.
The Cartoon Network cover letter is for the the job opening of being a designer. http://jobsatturner.com/atlanta/design/jobid8425411-designer-cartoon-network-jobs
The Roosterteeth cover is for two job openings, one is for the position of being a Production Artist http://www.roosterteeth.com/about/career-position/28 , and the other is for the Composer http://www.roosterteeth.com/about/career-position/64 , …. or heck i could also go for the 2D animation division too if i wanted…. http://www.roosterteeth.com/about/career-position/29
The descriptions of each job opening is in the links.