A few different postings indicated that some Sceptre users found success using Sony codes.
When Roku asks you for your TV manufacturer, just select Sony and go through all the codes and see if one works for you.
Settings/Remotes & Devices/Setup Remote for TV Control/ [select "change TV brand"]
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941