Let's say you have a 720p video from your phone.
Let's say you have Vegas.
Create a new project with custom parameters rather than a preset.
Set the project dimensions to 720 wide x 1280 high.
Import the video. Find a rotate function... which I assume Vegas has becasue every other video editor does.
Rotate the video.
Export (re -render) the video.
Done.
I do stuff like then when using video snippets for composting layers of motion picture visual effects... I rarely export "vertical" video for final output but I use rendered clips like this within a compositor (After Effects) and it works good.
The thing you have to do is get beyond the preset project and export parameters and use custom dimensions and some programs hide these to make stuff seem easier for routine users.
best regards,
mike