I'll point out a few things I saw in that vid. Sorry if some of my stuff seems jumbled or misplaced
I would only use G&W's roll to avoid something that could be devastating like a Dedede Fsmash or a Snake Fsmash. In that video you use it way too much and at the wrong times. Like I saw a few times where both you and your opponent kinda rolled away from each other or where you would roll into your opponent and then get knocked away. Instead of rolling away when he rolls I would try to follow him and pressure him with either the turtle or a dtilt.
G&W has a great approach game and it's usually a good idea to try to stay close and pressure people that have projectiles that the bucket cannot absorb (Link and Toon Link for example.) I noticed that you liked to use his key a lot when you were above your opponent. I would mix that up a bit to avoid getting predictable, like slow falling the key (just press down at anytime after he starts to fall) or even moving a bit to the side and trying to hit with a fair or bair.
For edgeguarding his dtilt works better near the ledge than his Dsmash. Plus if your opponent has an average recovery it's usually pretty safe/effective to jump off and try to gimp them. After Dthrows if you feel like you can't land a Dsmash then either dtilt or try to tech chase them and either grab them again or punish them with something.
I guess that overall the 3 things I think can be improved greatly with just a bit of practice are:
1. Rolling when necessary/using it less often.
2. Mixing up your approach, especially when coming from above.
3. Edge guarding.
