I feel your pain. The rostering for all our online tools and testing rosters pretty much defaulted to me as part of the "user account creation process". In the process, however, our IT team often ends up also doing a lot of Registrar work because we're the ones that get the notification when sync errors occur, and so we're the ones that end up cleaning up the bad data in the SIS in order to allow the syncs to complete correctly.
Over the years I've gotten quite savvy with Google Sheets as a result of creating the intricate web of sheets that we use to sync everything up. Our SIS recently added some more integrations with some of the tools we use, but I found that my Sheets did a better job of generating the roster sync files than the output we got from the SIS integration.
Some tools that I've added over the years to help with the process:
Sheetgo would probably do the trick, starts at $12 per month. It also has the bonus that all the data is stored on Google sheets, so if you stop paying for it you still have all your inventory and history saved. Smartsheet is another option, starting at $18 per month.
Disclaimer: I haven't actually used either myself, but they both have a free trial so you could try them out pretty easily. They're not dedicated inventory management solutions, but the cheapest inventory management software I could find was $50 a month, which is a lot to pay for a glorified spreadsheet.
Seems like Sheetgo is exactly what you are looking for. You can merge/consolidate multiple spreadsheets into one, even combining Excel, Google Sheets and CSV files. Check it out: https://www.sheetgo.com/
If you are looking for a relatively cheap way to manage your inventory, maybe check out this <strong>Inventory Template</strong> in Google Sheets.
It's free to use forever, in case you want to automate some processes it's $9 per month.
I can upgrade your plan for free if you want to test it. We launched these templates some time ago and we are looking for feedback. The template contains three spreadsheets "Check-in", "Check-out" and "Inventory Management Master Sheet" (the last one consolidates all data from sheet #1, #2 and it's a visual representation of your current stock). This solution is fully editable so you can change exactly everything you want, based on your business needs.
I'd recommend you to try Sheetgo Inventory Template in Google Sheets. It's fully automated and easy to set up. Just fill out "check-in", "check-out" input spreadsheets, run a workflow - automation and all your current inventory stock will be presented within a dashboard. There is also a way to make the template customized to your needs.