My understanding says,
Roadshow is an onsite event (a series of event actually) that we are doing in multiple cities to take company's message or brand awareness or product/services knowledge awareness.
Tradeshow is also an onsite single event (an exhibition kind of) where business in a particular industry promote their products and services. For example: Trade fair, education fair, auto expo etc.
And what is the similarity between two is that they both are onsite event (you would need to create event type program in marketo) and in the both events you can use checkin app and follow the same process. Just to maintain separate status two channels have been created.
Am a right or missing something?