They don't have to notify the public ahead of time in Canada, although they do usually publicize around holidays and such that there will be checkpoints, but they don't say where. It's just that naturally they tended to set them up on the higher traffic routes.
What you call probable cause does not meet the legal definition. For most of your country's history they would have been considered unconstitutional, just like asset forfeiture. The fact that some judges have stretched the meaning of the constitution to allow them doesn't make them right, does it? But I'll leave that argument to your countrymen. In this country they are perfectly constitutional and legal, but I still think they are a poor use of police resources, in most cases. Sometimes, for example on the main route out of an event, like the stock car races, where there's good reason to believe many intoxicated people might be hitting the road, I think they're useful.
What I call probable cause is not required for roadblocks. SCOTUS has also ruled on that here. Roadblocks are fine so long as they adopt proper protocals.
I would not call a license an asset, you do not own it, the state does. Therefor it is their asset to afford you or not.
I think we agree that roadblocks should be used in a targetted way that would see them being as beneficial as they can be when used.