Flex, Peacock Premium and Roku

Right now I have XFinity Internet only. I keep getting offers to get Flex for free. I've resisted because I already have Roku and Fire TV.

I tried to link my Peacock account with my XFinity account to access Peacock Premium but it failed as I don't have the right XFinity service.

My question... if I get the Flex, can I then link Peacock to XFinity to get the Peacock Premium for free and then watch it through the Roku and just avoid even running the Flex box?