All of the sudden last night my YouTube TV & YouTube apps quit loading on my Roku TV saying "not enough space". I tried all the usual suggestions (update, removed unused apps, etc) to no avail. I finally found a solution on www.streamersworld.com that solved this issue. Turns out the cache needed to be emptied. Here's how:
On the Roku remote do the following:
Hit HOME key 5 times
UP one time
REWIND two times
FAST FORWARD two times
If done correctly, the screen will go black after a few seconds. Wait a few minutes and Roku will restart. Mine worked after that.