Re-rolling Content
Following requests from the community, this version of Hexroll allows re-rolling content. In fact, the entire generation engine was re-written for this purpose.
First, make sure you are in crawl mode.
Next, unlock the content by clicking the lock symbol in the header.

You will then be able to reroll the current entity by clicking the dice symbol in the header:

or reroll other linked entities by clicking any of the dice symbols inside the text:

Note
Re-rolling entities might have a cascading effect on other parts of your sandbox. For example, if you re-roll a dungeon, any lost item or captive NPC will likely be relocated to other dungeons.