Cute flock!! What exactly are you asking by do you need a rooster? Roosters are very good flock guards and will give their lives when defending against a predator. They are also good alarm clocks and will provide fertilization in the hens' eggs. (Which means they can hatch chicks.) However, roosters are VERY loud. Crowing all day long. They also can be mean and tend to be bossy. (That all depends on breed though.) Hens do not need a rooster to lay eggs. You, again, only need a rooster for fertile eggs that will hatch chicks after 21 days of incubation.
After looking at your birds it looks as if you may have one RIR rooster. How old are your birds?