(This is an explanation on how certain pikmin live. This isn't canon and you're free to add elements to what is written here to your characters, stories, etc. (credit is not required but appreciated))

The Basics:

'Rogue' pikmin are pikmin that choose to live off by themselves. Most of these pikmin are living like this for a reason. Many popular examples are pikmin that runaways (like the leaders are bad, they're being bullied, someone's out to kill them, etc), ones that were exiled, ones that are soul searching (or something of the sort), or ones that had their onion was destroyed.

Many pikmin don't know how to live like this properly since its a sudden decision, though, many plan it out and/or learn from others. Sometimes, these pikmin will form groups with each other (or convince pikmin with onions and captains to live with them, especially if they had a bad experience with onions/captains) or return to their onion/captains or find a new onion/captain to follow. Why a pikmin would want to become rouge varies from pikmin to pikmin.

Sheltered Vs Wanderering:

There's two kinds of ways a pikmin can go rogue; sheltered and wandering.

Sheltered:

Sheltered pikmin live in a home of sorts. Usually caves, hollowed out trees, abandoned buildings (either from human times, built by captains, or built by pikmin if your canon has buildings on PNF-404), and so on. They can even build houses if they really want! The locations the pikmin call home are often referred as homesteads. These pikmin often store things like food and weapons in their building of choice.

Wandering:

Also called Wanderers, wandering pikmin are what you expect; its pikmin that choose to explore instead of staying in one place. They often have have a small weapon and a backpack with them at all times (if you want). Its more dangerous but more worth it to the pikmin who choose to wander (sightseeing is a common motivation).

Not all rogue pikmin fit the stereotypes, if they don't, they are a mixture of both (example: one who is pretty much a wanderer, but will often set of camp for several days on end).

Necessities:

To survive, these pikmin need things such as shelter/places to sleep and food. I'll probably make wiki entries detailing each of these but I'll put more simple versions on what they need here:

Food:

There's many easy to kill creatures on Earth (PNF-404), like sheargrubs and spectralids. Though, some pikmin can and will eat fruit, vegetables, and other kinds of plants as well or instead of meat.

Shelter:

Finding shelter is probably the second most important thing to have. Without it, monsters would kill the rogue pikmin. Common shelters include trees (on a branch or hollowed out) and caves.

Protection (Weapons):

Its recommended to attack using home-made weapons instead of repeatedly hitting the prey over and over as weapons typically can do more than slaps. Things like swords, spears, daggers, bows, knives, etc. Some pikmin decide to dedicate themselves to making weapons but they are rare (but are really useful if a pikmin could earn their trust). (This isn't necessary since pikmin don't have to be that intelligent enough in your story's canon)

Storage:

Bags and backpacks are probably one of you're best friends if you're a (wandering) rogue pikmin. They need something to carry their things in after all. (This isn't necessary since pikmin don't have to be that intelligent enough in your story's canon) Sheltereds who create homesteads will store items in their home of choice or make boxes, chests, or other things to store things (again, not necessary if the pikmin in your au aren't that intelligent to make boxes and such)