The point where a sheet turns expensive
The sheet does not fail loudly. It fails through small leaks: a second installment nobody chased that turns into a refund conversation, a rooming change entered in one tab but not the other, a supplier headcount sent from a stale number, a passport scan still sitting in a shared folder eleven months after the trip ended.
Price those leaks once. One missed final payment on a trip priced in the low thousands, or one night of a double room you guaranteed and could not fill, wipes out several seasons of software cost. That arithmetic is why organizers move, not because the sheet is inelegant.
What is genuinely better about a spreadsheet
A sheet holds the odd cases without complaint. The traveler who is paying in four unequal amounts because of her pension schedule, the friend of a friend joining for only the second week, the cost line for a driver you booked in cash. You can add a column for anything at any time and nothing objects.
It is also portable and permanent in a way that matters. You will still be able to open a 2019 roster in ten years. Any tool you choose should let you export to that same format, which is why the export in RoamRoster is a plain spreadsheet of the roster, the payments and the rooming decisions rather than something you can only read inside the product.
Keeping the sheet for what it is good at
Plenty of organizers run both, and it is a sensible arrangement. The trip budget stays in a sheet, because budgeting a departure means modeling exchange rates, supplier quotes, your own airfare and a contingency line, and a spreadsheet is still the best tool ever built for that.
The roster moves out of the sheet, because the roster is where the repetitive human work lives: the chasing, the pairing, the collecting, the messaging. Split it that way and each tool does what it is actually good at, and you stop maintaining a headcount in two places at once.