Don’t you have friends/family members who would do this for you? IME, just about anyone you speak with will be influenced by their personal choices/preferences/prejudices. If you go with a store, they will recommend what they sell. If you go with an Apple fan/hater, the will recommend/disparage Apple…
We had considered getting a cheap laptop and keeping it plugged into our TV. My wife went with the AppleTV, realizing it was essentially a computer. We did this step as a part of a reworking of our entire tech - I bought a new laptop, I got all my data off of an computer and an old Droid device, we decided to consolidate our cloud usage… We realized it was very easy to just keep accumulating data and opening new accounts, but that the various providers did not necessarily want to make it easy for us to transfer the data later on. So one reason we went w/ AppleTV is that we have become fully Apple in our tech. Many people would say we are wasting our money for inferior product, but we can afford it and it seems to work for us.
Another thing is, to some extent, your end result will be limited by your weakest link. So, you might get a new Roku, then you’ll need new cables, then will you want a new TV? When we used our computer to stream TV, I think we had crappy cables, as the TV image would periodically crap out. My new laptop required a special adapter to connect to the TV - or whatever other device.
You may wish to decide whether you want to pursue incremental steps, or jump in whole hog. For example, I THINK we had SOME capability thru our Blu-ray player, but we had the $ and preferred to get a new device. And we have an old digital antenna which pulls down quite a bit of stuff.