Streets of Rogue's workshop can be found here:
https://node2.projectplanet.cn/@steamcommunity.com/app/512900/workshop/

The page should be visible once you join this group.

For info on how to enable the level editor, see here:
https://node2.projectplanet.cn/@steamcommunity.com/games/512900/partnerevents/view/1634173213748492016

Please post your feedback to this thread, or send through the in-game feedback form:
https://node2.projectplanet.cn/@steamcommunity.com/app/512900/discussions/0/1658943011696209780/