Have you tried if the bootstrap class transform: rotate(degrees) works?
In theory all you need is CSS. Here is a good stackoverflow post that discusses your problem. Keep in mind that the behavior might be different in different browsers. Additionaly here is an MDN reference article on the input range type, where they also use the transform property.
I’m not sure which widget you are using so I can’t reproduce the issue, but in one of my apps I’m also using a vertical slider for mobile. I managed to make this work with a plain native range input (I used the number input widget of Mendix and changed the type with this widget) and the CSS that I took from the stackoverflow post.