Okay so we have a Samsung "Smart tv" I subscribe to Netflix, Hulu/ Disney+,Prime video.
We get Peacock, etc.... included with the TV,
What extra would I get with Roku device, and is it a monthly charge?
I would like to get the SYFY channel, but don't want to pay the extra subscription charge for 1-2 shows.
I will recommend ROKU. I have two of them. After the initial cost (and I would recommend somewhere around $70 and up - the cheap sticks suck), there need not be any other cost. However, many channels are subscription based - I carry no subscriptions accessed through the ROKU, and find enough to make it enjoyable.
However, your subscriptions will transfer just fine into the ROKU - Depending on the site, you may only have to plug in a username and password into the Roku, or 'activate' the subscription on a new machine... somewhat various and fiddley...but relatively painless after done.
Sci-Fi channel is subscription based on the ROKU, just like it is everywhere.
THE REAL way forward, as I have said so many times, is to learn to find what you want online with a laptop or something... If you can get to it at all, you can get to it on the unguarded internet... Add to that the options you get with a VPN service (can make your PC seem to be in another country which gives you things you can't get here), and the bandit sites (*cough* putlocker *cough*) and there is very little you can;t access one way or another...
At that point, when you have mastered that, hook a PC up to your TV - It can be a pretty crappy secondary machine, or something you found at a flea market... If it has Win10, more than 2 cores, and 16g RAM it will work. You may need to buy a vid card to get DVI or HDMI out (to physically hook to a TV), you may need a wireless NIC (to 'hook' to internet), and you will need a logitech wireless keyboard/glidepad (wallyworld, $30) to operate it from your easy chair...
Now your TV is no different than the laptop (or whatever) you are used to using to cruise around... ANY browser will let you 'cast' to the TV, so you can find what you want in your phone or laptop and providing you are using the same browser in all, you can send the tab to the TV to watch in comfort.
I pay my end of a family account at Netflix... 70 bucks a year... I can get at Prime (because I already pay for it for shipping)... and that is all. All the rest I just go find online.