100% agree with LostSoul. Killing your way in is an option and starting with MommyDearest is typically the best place to start. There are two things that change if you kill your way in. As LostSoul points out, you can just walk out after killing Roost. Also, when you go to Roost, you won't be able to do any dialog. This is only an issue if you have Sebeile or Ifan in your party.