There's a legend that says that Amaru, ancient god with the shape of a snake, emerged from the bottom of a lake and turned into a bull, an animal characterized by its strength and size which is always willing to help them plowing the soil. This brought fertility and wealth.
In order to honor Pachamama (or Mother Earth), the natives celebrate a ceremony in which they make lacerations on a bulls skin to make it bleed (without killing it), then put hot peppers (rocoto) on the bull's nose and set it free. This makes the bull run freely towards the sacred mountains while spilling its blood on the soil, which was believed to make it fertile.
In order to obtain fertility, some people put little ceramic bulls on their roofs when the houses are first blessed. This sculpture is known as Torito de Pucará (Pucará is a town where the bulls were originally sold).
The bull represents happiness, wealth and fertility, while the cross keeps the bad spirits away. The ladder is considered a part of the cross (when Jesus was removed from it) and the sorts represent abundance, wealth. The water jugs may represent fertility too.
Some people also put miniature churches on top of their roof with a similar purpose. The cross is usually made of iron to stop the negative energies of lightning.
The arrangement of the ceramic sculptures may vary for different towns and home owners. Other arrangements may include more bulls (if the homeowner raises animals or cattle), jugs with flowers (if the homeowners are farmers) or miniature ceramic musicians (if the homeowners are musicians).
This is just one of the many examples from the mixture of Catholic and native religions.
I'm from Peru