A jail roster answers where someone is. It does not answer what happens to them. For that you need the court record, which is a separate system with separate rules.
The clerk of court is the authority
Every county has a clerk of court, or an equivalent office, that maintains case files and calendars. That office is the authoritative source for hearing dates, filings and dispositions. Many publish an online case search; where none exists, a phone call to the criminal division works.
What you need to search
A full legal name, spelled as it appears on the roster, is the minimum. A date of birth narrows common names considerably. A case number, if you have it, is best. Note that the name on the court file matches the booking record, which may not match how the person is normally known.
Which court
Criminal cases are split by severity. Minor offences are usually heard in a lower court — district, municipal, or magistrate depending on the state. Serious felonies move to the higher trial court, often after a preliminary hearing or grand jury. A case can appear in one system early and another later, which is a frequent source of confusion when searching.
Hearing types you will see
The first appearance or arraignment covers charges, rights and release conditions. A preliminary hearing tests whether there is enough evidence to proceed. Pretrial conferences and motion hearings handle scheduling and legal arguments. Most cases end in a plea hearing rather than a trial.
Dates move constantly
Continuances are routine. A date confirmed last week may be gone this week. Check again within a day or two of any hearing you plan to attend, and confirm the courtroom as well as the time — courtrooms are reassigned frequently.
Attending
Criminal hearings are generally open to the public. Arrive early, expect security screening, silence your phone entirely, and dress as you would for a formal appointment. Do not attempt to speak to the judge or prosecutor. If the defendant is represented, direct questions to their attorney.
When online records show nothing
A missing case is not necessarily an error. Charges may not have been filed yet, the case may be sealed, juvenile matters are generally not public, and some counties simply do not publish online. The clerk's office can confirm what exists.
What a court record will not tell you
It will not explain what the evidence is, predict an outcome, or substitute for legal advice. If the decisions matter — and in a criminal case they do — that requires an attorney licensed in that state.