I used Gu roctane last season and found the product to be inconsistent from a quality control standpoint. Some of the canisters I had made me pee like an utterly insane amount to the point I think it dehydrated me during IMLP. No joke (TMI) I think I peed 8 times on the bike at LP. Maybe it was something else but I started to notice this using the product in my training but ignored it. I also found it a little too carbohydrate dense and too sugary tasting. I used a similar approach to what you said: 2x concentration and two bottles at special needs (4 bottles total) and water at aid stations. I am now using gatorade endurance and planning to use solid food on the bike for the extra calories (cliff bars) instead of gels. My takeaway from using roctane last season is that its OK for shorter distance racing (sprint-OLY) but not something I will use again for 70.3 and IM.

So, yes, its a "decent" plan but I think you want a "better" plan or a "proven" plan for nutrition. I think it's easier to use what is on course and thats the direction I've decided to go. Anything that makes race day less complicated is good in my opinion.

Don’t forget sodium. A bottle of Gatorade Endurance has 310 mg of sodium. Some evidence shows you need more than 3 times that.
You didn’t mention how long your ride is going to take you but you certainly can put 2 bottles in your special needs bag, that’s what I do.

The best plan is to have multiple options--I'd say be prepared for as many scenarios as possible. What if you eject one of your bottles of roctane and it explodes? You should know your sweat rate, how many carbs you're trying to consume, what's in everything you carry with your and on course, and be able to do some math on course in case your plan goes wrong.

As a poster above said, Gatorade endurance has 300 mg of sodium, but that's per SERVING. An on course bottle is two servings so a bottle of Gatorade is 44 g carbs and 620 mg sodium (https://www.gatorade.com/...ormula/bottle/orange). It's important to know all these little details.

I've done everything from concentrated bottles to living off the course in IM races, and the best advice I can give you is practice your race nutrition starting a few months out and be able to adapt to anything race day can throw at you.