Lipid rafts are a region of the plasma membrane. They move freely in the membrane but are more tightly packed than the lipid bilayer. Therefore, lipid raft regions will have a higher transition temperature compared to the rest of the membrane.
Lipid rafts are a micro-domain of the plasma membrane. In this micro-domain, sphingo-phospholipids, cholesterol and protein receptors are present. These are responsible for membrane fluidity to a very great extent. Now, if you increase unsaturated fats, there should be an increase in fluidity of lipid raft.