Not easy. You can rotate a source by right-click->Transform->Edit... and edit the Rotation angle. But this is very static and does not do any tilt as 3D effect. For this, you need plugins. I know there are such plugins, but I don't remember any name currently. You will have to consult the Google search for this. Probably "obs plugin 3d tilt" or "obs plugin 3d rotate".
Such a plugin is probably implemented as filter, so you would be able to rotate text with it if you put the video you intend to tilt and the corresponding text into a group and apply the tilt/rotate filter to the group, so they are both rotated/tilted.
