I have an old tv. It says the TV output resolution is 480p. Will Ruko work with this type of tv?
Not with an HDMI input, no.
Roku used to sell models with composite output, but deprecated those a few years ago (the 3910 was the last model with composite in fall 2017).
You'd need an HDMI>Composite converter/adapter and connect it via RCA/composite.
You can get them for around $10-15 at amazon.com/walmart.com etc. (More expensive ones might have S-Video or Component output, if your TV supports that)
Here is a link that is pretty comprehensive regarding the different Roku devices and their capabilities.
Newer Roku devices will not, some older Roku devices will but will probably be unable to be updated. (If they currently are able to be updated.)
You can see if the Roku device you are looking at is capable of being updated (still supported) here.
Basically, time to get a new tv (or at least a newer used tv) if you really want to get the real benefits from a Roku device.