There are a couple of problems with guaranteeing specific rooms. The first one is technical: the method I use is not suitable for this. To generate a house I first create a floor plan (or plans if it's a multi-storey buildings), a set of rooms of varying sizes. Then I try to assign them "roles" - bathroom, kitchen etc. As a result, it may happen so that there is no suitable room to become a bathroom for example. There is a core set of "roles", which my algorithm kind of tries harder to assign, but...
Another problem is UI: creating a tag or a checkbox for each room type doesn't sound like an elegant solution :)
Hopefully, I'll find a way to resolve all this somehow, but I don't think it's a huge problem. After all, if you need a specific room to be present, you can any other room and rename it.