I checked the channel store, and while there are many golf related channels, none from the subscription service Golf Channel.
However, Roku does not create channels for other providers. Those providers must provide apps/channels for their own content. It's possible the Golf Channel has agreements with cable/satellite providers to not provide their own subscriptions to their service.
Looking at their web site (I see they are owned by NBC) all I see are TV providers listed as a source to watch their content. I do see the three major streaming TV providers listed: FuboTV, Sling TV and YouTube TV. All three of those services are available on Roku devices, so you could subscribe to one of those three and watch the content through their service. However, if you already have TV service that provides the Golf Channel, and your service doesn't offer a streaming channel (both Xfinity and Spectrum appear to have Roku channels) then there's no way to watch the content on a Roku other than screen mirroring a computer to your Roku.
Dan
Roku Community Streaming Expert
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