Johnson has a full no-trade clause. I highly doubt he would waive it for the Jets.
But I like the way you are going with this. Replace Trouba with a cheaper / younger player like Sergachev, and sweeten the deal by clearing cap room.
Instead of Johnson, what about JT Miller? He doesn't have a NTC, has played C in the past, has a bit more size and bite to his game, and still comes in at $5.25M.
Callahan also has a no-trade clause, but maybe he'd waive it if the Jets agreed to buy him out. Then he would re-sign with TB, or any other team he wants without losing much in salary.
Something like this?
To TB:
Trouba (6.75M)
Roslovic (0.9 M)
To Wpg:
Sergachev (0.9M)
J.T. Miller (5.3M)
Callahan (5.8M)
Pick (2020 1st or 2nd)
TB might still need to shed some salary, but it would have the net result of clearing about $4.3 million in cap space, while filling in their D with Trouba and Roslovic.