I was thinking about getting a new roku device and I'm wondering if once I put the new one on and add all my movie apps will I still be able to see that line under the stuff I've already watched still be there so I know where I left off or will it just look like I haven't watched it at all? You know how it shows you the episodes you've seen already, I'm worried all that will be gone and I wont know where I left off. Thanks
In general those things are tied to your account (either your Roku account or your account directly with the provider). Adding a new Roku device to the same Roku account and/or signing into the same provider (Netflix, Hulu, etc.) account should keep your status intact.
Tracking which shows/episodes you've watched is done by the individual channel apps for which you have established accounts. For any channel that tracks your viewing, your viewing history should be accessed on any Roku that is logged into the same channel account.