Taracan2-
Those inadequate memory warnings are often a symptom of the Roku memory cache getting corrupted. Deleting channel app after channel app does not make the warnings go away. Clearing the memory cache should cure the problem.
The easiest way to do this is to RESTART your Roku. (For Roku TV users reading this: if you have "Fast TV start" enabled, turning the TV off and back on just puts it into and out of a standby state and does NOT give you a complete restart, so use the methods below.)
Depending on your Roku model you'll find the "System restart" option under "Settings > System > Power", or on models without a Power option, under "Settings > System".
If a restart doesn't do it, or if you don't have sufficient control with the remote to navigate the Roku menus, you can also restart by pulling the power plug to the Roku for a few seconds then plugging it back in and waiting for it to restart.