I'm excited it sounds cool. I always thought that rogue one was the #1 position on the rogue squadron. I'm sure they referred to Antilles as Rogue one while looking for Han and Luke. I take that back he was rogue 2 he might have been rogue 1 in rotj. So it could take place during or after battle over endor. I'd be willing to bet its about Antilles he's the only pilot to survive both attacks on the Death stars and the battle of Hoth. He's also the only minor character to survive all 3 original movies.
In the films there was never any mention of "Rogue One" but rather "Rogue Leader". Actually, in all the battles we see, its always "Red Leader" or "Gold Leader" etc. There has never been a designation of "Red 1" or "Gold 1" even though "Rogue One" is the same as "Rogue Leader" basically. In the films they always use "Leader" and not "1". Rogue One is the #1 position of the squadron.
The battle you might be referring to when they were looking for Han was the Battle of Gall from Shadows of the Empire. By then, Wedge had taken over Rogue Squadron. Luke temporarily flew with the squadron again, taking the Rogue Leader call sign. Wedge, who was already Rogue Leader, used Rogue One for the battle. At the Battle of Endor, Wedge renamed Rogue Squadron to Red Squadron, to honor those who had fallen at the Battle of Yavin. Shadows is part of EU, so it's being discarded unfortunately.
Seeing that the "One" call sign originated in the EU, and was never spoken in film, its possible it will be discarded. So like the quote I mentioned before, its unsure if "Rogue One" is referring to Rogue Squadron or something like Home One or Air Force One. It'll be interesting for sure. I know it might sound a bit confusing at first but I hope I did a good job explaining it lol. For all I know, we could be looking into it too much haha.
I talked it over with my friend today, he says it makes too much sense for it to not be about Rogue Squadron. Regardless we're both excited.
