For animals that live in groups, are there examples where all of them have the same role? For example, in animals we know there are bee queens or alpha, beta and omega mammals. But are there groups of animals where all the members have the same role? My question is aimed at 2 different groups actually, first animals in general (which includes reptiles, insects, etc.) and second to mammals only.
Yes, there are many examples. Those species are said to be gregarious. See below for examples.
Level of sociality
When it comes to social behaviour, it is common to categorize species into one of four categories: Solitary, gregarious, presocial, and eusocial.
Note that definitions may vary among authors and that there are limit cases that make the question of categorizing much richer than the simple definitions I am using below.
Solitary species are species where individuals mainly live alone and are independent of each other (They may still meet to mate, though).
Examples: fox, polar bear
Gregarious species are species that gather into a group but do not share any labour. Each individual is selfish. Such gregarious behaviour can be driven by safety (typically during migration), to taxis toward a resource, or any other reason that may cause these individuals to gather!
Note, when you say "have the same role," it is clear that different individuals may use different life strategies (like typically territorial males vs. sneaker males in birds).
Examples: wildbeest (during migration), many insects attracted to a given lightsource.
Presocial species are species that are gregarious and have a separation of labour but no separation of the the reproductive labour.
Examples: Humans, many hymenopterans, vampire bats
Eusocial species are species that have a separation of labour including separation of the reproductive labour.
Examples: Termites, ants, naked mole-rat