Ok, so, Biosphere 2 is a thing. It's approximately 3.14 acres in size (~137,000 square feet) and is a complete, functioning, stable, self-sufficient biosphere. So far the maximum number of people that have lived inside of it (and off the environment inside) is only eight and oxygen levels dropped to failure (of the experiment) levels after about 2 years. And the participants were on borderline-starvation diets.
Quoting the Wikipedia entry linked above, its five biome areas were a 1,900 square meter rainforest, an 850 square meter ocean with a coral reef, a 450 square meter mangrove wetlands, a 1,300 square meter savannah grassland, a 1,400 square meter fog desert, a 2,500 square meter agricultural system, a human habitat, and a below-ground infrastructure.
These numbers only add up to 1.96 acres, but I assume that the remaining 1.18 are accounted for in the human habitat and underground infrastructure (that didn't have numbers). However, these numbers give us something to work with.
At 8000 square meters per biome we can construct a volumetric section of "structure" that is 200 meters wide and 400 meters long (this is on the scale of a football stadium). For simplicity, we'll make this a cylindar with a radius of 100 meters, filling one side with dirt and underground infrastructure. Structural support will largely be on this "bottom" side as well.
Stringing 8 of these structures together into a ring we can create a toroidally shaped structure approximately 510 meters in radius. We can spin this at 1.32 rotations per minute and get ~1 G worth of artificial gravity, which due to the size of our structure will be within a nominal comfort zone (i.e. the difference in angular velocity between a human's head and a human's feet won't be terribly noticeable).
I can't find any numbers on how to calculate how strong the materials need to be in our construction, but as a non-engineer and non-physicist this seems at least within the realm of plausibility and good enough for story writing. Still, we're dealing with an amount of material weighing in near the 80,000 tonne (157,000,000 pounds) range and need to support it via tensile strength. And I'm just not sure how to even go about looking up the math needed to continue. If we're not constructing it as a space ship/station we don't even need to bother. It sits on the ground and covers an area the size of a dozen football stadiums. Large certainly, but still smaller than the TV studio portrayed on The Truman Show.
All in all this structure will probably sustain between 30 and 60 people indefinitely, figuring each person will need between 1000 and 2000 square meters worth of functioning biome to sustain the oxygen levels. Food will probably still be on the "starvation" end of the spectrum depending on the distribution of land devoted to agriculture vs. biome diversity and nutrient cycles. Onstensibly one acre feeds a person (~4000 square meters), but we could probably cram that in small with hydroponics, vertical farms, and skipping the "night" half of the day/night cycle. Use pink light to cut down on your power bill.