Dreams involving animals, especially in unusual settings, often symbolize different aspects of our emotions, relationships, and experiences. In your dream, the mammoths and other animals represent powerful forces or issues that may feel overwhelming in your waking life. Here are some interpretations of the key elements:

1. Mammoths: These large, ancient creatures could symbolize something significant from your past that is resurfacing, possibly a long-standing issue or emotion that feels massive and unmanageable.
2. Animals on the Roof: The animals walking on your roof might suggest that there are external pressures or influences in your life that you feel are encroaching upon your personal space or home environment.
3. Swimming in a Pond: Water often represents emotions. Swimming in a pond with your children indicates a nurturing role and suggests you may be navigating your feelings while also caring for your loved ones.
4. Roof Collapse: This dramatic event could symbolize a fear of instability or disruption in your life, particularly concerning your home or family life. It may reflect anxiety about changes that seem out of your control.
5. Daughter's Friend: The fact that your daughter's friend was unharmed may indicate a sense of relief or that, despite chaos, your loved ones are safe. It could also suggest a protective instinct regarding your family and their well-being.

Overall, this dream may point to feelings of being overwhelmed by responsibilities or external pressures, and a need to address or confront significant issues in your life. It might be helpful to reflect on any stressors you are currently facing and consider ways to regain a sense of control or stability.