Each roof tile is one small piece of shelter, so a slipped or missing tile is read as a gap in your protection. Dream books link it to small vulnerabilities worth tending before they grow.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.