Some of it is complicated, but converting a roster bonus to a signing bonus is not too bad.
Using Goff's contract as an example, numbers from [
overthecap.com]. As it stands his cap hits for the next 5 years are:
2020 $36M
2021 $32.5M
2022 $30.5M
2023 $30M
2024 $26M
He is due a $21M roster bonus in 2020: if he's in the roster when the 2020 league season starts he gets $21M and it all counts against the 2020 cap as part of that $36M.
Suppose they change that roster bonus to a signing bonus. Goff would still get $21M next year, but instead of it all counting against the 2020 cap it would be spread equally over all 5 years, $4.2M a year.
His cap hit for 2020 would drop from $36M to $19.2M, but his cap hit for the other 4 years would increase by $4.2M a year. The cap hits from that restructured contract would look like this:
2020 $19.2M
2021 $36.7M
2022 $34.7M
2023 $34.2M
2024 $30.2M
Note1: the total cap hit is the same either way - $155M - the only difference is how it is accounted for.
Note2: there are other ways to restructure. One example would be to convert $10M of the roster bonus to a signing bonus. Again, Goff would get all $21M next year, but $8M would come off the 2020 cap and $2M would get added to each of the other 4 years.
AlbaNY_Ram
