Pick up a weapon when movement is 0

Question

In dnd 5e there are some interactions with objects that can be performed as part of movement in combat but can those action be performed freely if the movement is reduced to 0 by a condition or a class-feature?

For example, can a rogue pick up a crossbow and then use steady-aim? Or a character that has been disarmed and restrained can pick up the weapon if it's right at his feets?

If they can, will this operation be free or will an action be necessary to perform it since they lack their movement speed is 0 and so they don't have movement to perform it?

Answer 1

You can pick something up when your movement is 0

Having a movement of zero does not mean that you are paralyzed - it means only that you cannot change your lateral position relative to other creatures and objects (if you are playing on a grid, we could say it means you cannot change your space).

The 2016 PHB errata says:

Is standing up from prone considered moving? Standing up costs movement but moves you nowhere. When the game refers to you moving, it means moving some distance. It doesn’t mean making a gesture or standing up in place. To move while prone, you crawl or use magic (PH, 191).

So long as you don't have to move a distance to pick up the item, you can do so freely, subject to the rules for interacting with objects, even if you currently have no movement remaining or if your movement or speed has been set to 0.