Yes: rats are adaptable, and their own kind supplies the friendship
A fancy rat can live happily in a home with other kinds of pets, because rats are unusually adaptable, curious animals that take household life in their stride. A rat does not need the dog or cat to be its friend; it needs at least one other rat, since this is a profoundly social species that sleeps in contact and grooms its cage mates. With rat companionship covered, the other pets become a management question rather than an emotional one. Many rat owners keep dogs and cats successfully for years on a simple system of a secure cage, a rat room with a door, and roam times that never overlap with the predators' access.
The cage is the rats' castle, and it must not be besieged
A fancy rat's cage in a multi-pet home should be tall, barred closely enough that a cat's paw cannot reach a sleeping rat, and heavy or fixed enough that a boisterous dog cannot shove it. Rats love hammocks slung near the bars, which is exactly where a paw can reach, so if a cat has access to the room, position the cage so the cat cannot sit beside or above it, or keep the room's door closed as the standing rule. Dogs that bark at the cage or lunge when a rat moves need training and distance, not repeated exposure at the bars, because a rat colony living under daily siege shows it in bar-chewing, hiding, and squabbles among themselves.
Free-roam time is where separation does the work
The highest-risk hour in a rat-owning multi-pet home is free-roam, and it is also the hour rats love most. Give fancy rats their roam in a rat-proofed room with the door closed and every dog, cat, and other predator pet shut out for the whole session, then do a headcount of every rat back into the cage before the door opens again. Rats slip behind furniture and into upholstery, so the room needs its gaps blocked and its cables protected, and nobody should open the door mid-session without announcing themselves. A dog scratching at the roam-room door is a reason to move the dog, not to shorten the rats' time by default every day.
Smell, sound, and the rats' famous nerves
Fancy rats have sensitive respiratory systems, so sharing air with the household cuts both ways in a multi-pet home. Keep the rat cage away from litter trays, scented candles, and the dog's freshly bathed, strongly perfumed corner of the house, since airborne irritants are a real health cost to rats. Noise matters less to rats than to shyer species, but a cage beside a television at full volume or a door that slams hourly still erodes their rest. Rats also read your handling: hands that smell strongly of the cat can make a nervous rat flinch, so a quick hand wash before handling keeps interactions easy for everyone.
Coordination is what makes the mixed home run smoothly
The households where fancy rats and other pets coexist best treat the logistics as a shared rota rather than one person's vigilance. Everyone knows the roam hours, the door rule, which treats in the kitchen are rat-safe and which are not, and what to do if a rat is ever found out of its room: close doors, confine the other pets, then retrieve the rat calmly. Children learn that rats and the dog are never carried into the same room to meet, however cute the idea sounds. KinsLe's Family Sharing keeps your fancy rats' roam schedule, cage rules, and found-a-rat steps on one household profile, so the dog's walkers and the rats' roamers are finally reading from the same page.