Buy some tin. If you want to make several tin roosters, get enough tin for the sizes you want to make. A small rooster may only require one square foot or less, while a large one more than two. Most home improvement or arts and crafts stores have tin. A 6" W x 12" L sheet is only a few dollars.
Borrow or buy a metal cutter. A powered cutter costs about $200, while a hand cutter only $75. Using a powered cutter is faster, while a hand cutter allows you more precision.
Buy paint is whatever colors you want your rooster to be. White, red, yellow, orange and black are good to mimic a real rooster colors. Make sure the paint is suited for outdoor use. Small paintbrushes are best suited for the painting.
Buy or make a stencil. Arts and crafts stores may have one. If you are good at drawing, then draw one. If not, print a picture of a rooster and outline it on the tin. After the first rooster is made, it can be used as the stencil.
Buy steel rods. These will be used to keep the rooster above ground.
Find a clear area. It should be clean, allow you plenty of room and have a table. Place your metal cutter, paint, tin sheets, brushes, stencil, and any other supplies on the table for easy access. Put them on the opposite end of the table from where the cutting is being done.
Outline the rooster on a sheet of tin. Use a thin permanent marker. Now cut away excess tin, as to allow you easier access to the outline.
Cut the rooster. Follow the along the outline exactly, cutting on the line. Take your time with this. After the rooster is cut, you can smooth the edges if you wish. Repeat this process for however many roosters you want.
Paint the rooster. If you wish to do this, then start by painting the tin white. Paint the beak and feet yellow or orange. The eyes should be black. Wings are painted red. Use as much detail as you like. You can paint one or both sides.
Attach the steel rods. This is most effectively done by a spot weld, but it can be bolted or screwed on. Alternatively, use a straight scrap of tin. Cut a small hole in it, as well as the rooster. Then bolt them together.