Roku devices are portable. Just plug it into your friend's/family's TV via HDMI and connect to their network. Make sure to bring your remote with you. (unless they have a Roku remote that can pair to your device).
The only issue I would have with taking my Roku Ultra to a family member's house is that it's expensive and I wouldn't want to forget it and be without TV or end up having it broken. So, what I did was I bought a Roku Express, which currently sells for $25 through Roku's website. You could get the 4K for a little more. (I bought the Plus at Walmart since I have an old TV.) What's nice about this is that it's slim so it packs up nicely and it uses a USB power supply so you can use it with any USB cord and USB plug if you forget to pack that (just don't forget to bring the remote). You would just add your account to it which will install all your channels (out of order, unfortunately) and if needed, log in to your accounts. Just make sure to plug it into an outlet and not into the USB on the TV because that's not powerful enough. Then if a young child cousin stomps it, or dissects it, or buries it, or blows it up, or sends it to another dimension, you still have your Roku Ultra safe and sound at your home. And it's always nice to have a backup Roku in the event something were to happen to my main Roku.
Also, be advised that if you have live TV through Hulu -- this won't work since Hulu anchors this to your home's IP. If you have live TV through YouTube TV or DirectTV stream, then you should be fine.
