I've had a Roku box for about 4 years and use it mainly to access my Netflix queue. It's not like having a cable box where everything is in one place to search. You use it as an access point or gateway for a number of services. I know if no built-in, universal search. The best suggestions I can make are:
1) They should contact Roku tech support to ask specific questions about what it is they want to do exactly.
2) Go to the web site www.clicker.com which has a search function and universal queue that works across platforms.

Here is a link that might be useful: Roku Support

I have a Roku box ordered. It should get here any day now.
When I get it set up and start using it I should be
able to help with this problem. I only have Netflix, tho.

Pooh Bear

I meant to say: "I know of no built-in, universal source."

Having cleaned up that typo, I have one other reference for you. Below is an article and short video that lays out pretty well where and how you can go to get what. Again, it doesn't solve your basic issue of not having a built-in search for everything, but at least it's a road map to where the content is and explains what streaming devices like Roku can do.

Here is a link that might be useful: TV program sources and devices

Looks like you can search each channel, but not all at once.
I can search the Netflix channel by clicking the Home button
on the remote (top right) then clicking on the Netflix channel,
then on the remote click the down arrow to highlight the search,
and then search the entire streaming Netflix library from there.

Pooh Bear

After you get the first screen when you bring Roku up tab over to channel store and they will give you all the channels that are currently available via Roku.