The rules do not say
The DMG only says "unleashing that magic requires using an action to read the scroll."
The image of a caster reading a scroll from a lectern (usually carved with dragons and gargoyles and the like) is common in fiction so I would rule that you don't have to physically touch the scroll.
I would, however, rule that you have to physically eyeball the scroll. THatThat would avoid any "long range scroll" highjinkshigh-jinks.