@jkeen
A little more information might be helpful.
Since you can create a Routine (I think that's what Google Assistant calls them) to launch a Roku app, it may depend on the app. Some news apps, for instance, start playing as soon as you launch them. So, I'm assuming that's not what you're talking about, as you would simply have asked if Google Assistant can launch an app.
So, details will help. What app? And that matters as different apps require different processes to launch and play content. Playing news from, say, Roku Channel isn't the same steps as playing news from, say, Sling TV.
DBDukes
Roku Community Streaming Expert
Note: I am not a Roku employee.
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