Yes i have an idea. Your rooster have a respiratory infection that is probably viral and very similar to a common cold. Chooks have their own version of the common cold.
Like us they get a stuffy nose but their anatomy is slightly different to us and their sinus is close to and under the eyes with a direct passage into the eye socket. The swollen and sore eyes along with the froth is coming from the sinus. The easiest thing is to make up a warm saline solution (teaspoon of salt in a cup of warm water - no stronger than that.) and flush and wipe his eyes at least several times a day until he is getting better.
Mostly this respiratory infection runs its course and passes without further intervention. However on occasions the muck in the sinus becomes infected with bacteria and then it may require antibiotics to help it clear up. At this stage, from what you describe, there is no indication of a secondary bacteria infection.
Thanks for the info Mike, that's great. I'll try that straight away.