I've seen this question asked about 4e, and I think I've found the passage in the 5e PHB that answers the question, but I'd like to make sure I understand this correctly before I impose it on my game.
The question is can sheathing one weapon and drawing another be part of the same "free action", or does this take a full action?
The PHB (page 190)
You can also interact with one object or feature of the environment for free, during either your move or your action. For example […] you could draw your weapon as part of the same action you use to attack.
If you want to interact with a second object, you need to use your action. Some magic items and other special objects always require an action to use, as stated
in their descriptions.
As a bonus question, what do you think about a Rogue using their "use object" bonus action to draw a weapon after using their free action to sheath one, leaving a standard action and movement action left to be used.