Is sharing a room worth the savings in SF?
Compare the savings to the costs you will actually feel: disrupted sleep, fewer places to work, less storage, harder dating, and the effort of coordinating every day. Then compare it to what the savings would buy: debt payoff, an emergency fund, shorter commute, or time to build a career.
The arrangement is more likely to work when the two people have compatible schedules, enough storage, a stable lease, and an agreed exit plan. It is less likely to work if either person needs frequent solitude, works irregular hours, or cannot discuss boundaries.
Try to calculate a date when the trade-off will be reviewed. Sharing a room for a defined six-month goal is different from doing it indefinitely because no one made a plan.
The answer is personal. Honesty about your needs is the useful math.