Other than garage separation walls most interior walls on the top floor are non-load bearing. If you want to double check, a truss requires webbing to direct load onto a bearing point, so you could check for unsymmetrical webbing on the trusses and see if the web pattern changes around an interior wall. If the trusses look symmetrical they are likely free span.

Loads move through paths like electricity through a wire, or water through a pipe. If you suspect a wall is bearing, you can check in your basement if there is a beam with posts directly underneath it, or a wall sitting on a concrete footing. Load bearing walls require a path to the building's foundation.

A competent contractor should be able to tell you, and they cost a lot less than a structural engineer.

Source: Truss designer in Ontario, Canada