data in form of GZIP from server

We are trying to Implement compression on server side for Large JSON.Is their any other way to fetch GZIP based request and get JSON from it.

Most servers I know of have gzip enabled by default.
What you might consider is using some kind of paging for your data - so you can make multiple transfers of the data you need, instead of using one large piece.
Also, if you have access to the JSON feed itself, you could lower the size by having the roku code dynamically alter/create the extra fields where possible - for alternate bitrate streams, filenames, etc.
Rather than having the JSON list a separate tag for hours, and a separate tag for minutes, if you can combine those, the filesize will be smaller, resulting in a faster transfer – like rather than having
hours: 2
minutes: 16

if you had
minutes:136

That saves some bytes there.

If you’re using roURLtransfer, make sure you EnableEncodings.

-JT