Set file-manager used by "Open Folder"

[asymptotic]

How to set file-manager used by "Open Folder"?
On my machine, Transmission 's "Open Folder" menu sometimes use firefox to open folders.
I want to set it to another filer-manager, such as rox-filer.
How to achieve this?

Thanks.
Hu

[asymptotic]

Does anyone know this?

Thanks for your help.