The Epson driver for the 3880 has a length limit of around 950mm, I don’t recall the exact number but it’s fairly close to that. The limit is enforced in the driver. A RIP like QTR bypasses the driver and so doesn’t hit that limit. If you want to print colour longer than the limit, colour RIPs will generally enable this. I’ve used Printfab, but others will do it too. There is usually some kind of length limit in the RIP, but it’s probably longer than most rolls. As others have said, custom page sizes are your friend.
Regarding curl, if you’ve ever used a printer with a roll paper option (which the 3880 didn’t have), you’ll know that there’s always a leading margin of a couple of inches. I found out the hard way when printing on a long sheet cut from a roll on the 3880 why this is. The printer does this so that the leading edge of the paper is under the exit rollers before printing starts, preventing head strikes from paper curl. The same logic applies at the trailing edge, but is less obvious on a printer with a roll option, as inherently there’s a very long trailing edge. If you can’t flatten the paper, which can be difficult, I recommend cutting an extra few inches so that you have both a leading and trailing margin of 2".