From what I can tell, Trom is available from viaplay. As with a lot, if not all, premium subscriptions that The Roku Channel offers, there's two ways to subscribe to this provider. You can subscribe through Roku, which often comes with restrictions like you can only use the subscription on Roku devices and/or only through The Roku Channel, or you can subscribe directly with viaplay and use their stand-alone Roku channel/app and use that subscription on any device you like.
It looks like if you go to their website they offer a 7-day free trial.
https://viaplay.com/us-en/
Their stand-alone channel/app:
https://channelstore.roku.com/details/ded1b4cdd114876ab216a5a29ed3442d/viaplay
Occasionally, what some providers offer through The Roku Channel differs from what they offer through their stand-alone channel/app, but I think that's unusual. I would expect Trom to be available either way you subscribe, but you may have to research it to be sure.
Either way you subscribe, you'd have access to more than just Trom.
Subscriptions on or through Roku can be confusing, so don't hesitate to ask questions. I or someone else will do our best to answer them.
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