The Supreme Court ruled yesterday that employers are not obligated to change employes' work schedules or allow them to make up lost pay resulting from service in an armed forces reserve unit.

In a 5-to-4 decision the justices affirmed a lower court decision that although a reservist cannot be denied employment or promotions because he has to serve in the reserves, an employer is not required to allow a reservist to make up lost wages at a later date. Nothing in yesterday's decision would prevent an employer from allowing a reservist to make up lost pay.

In another case the court, in an 8-to-1 judgement, said federal inspectors have the right to make inspections without a search warrant at the nation's mines. The court held that unlike searches of private homes, which generally require warrents to comply with the Fourth Amendment protection against unreasonable searches, laws authorizing warrantless searches of commercial property don't necessarily violate that amendment.

In the reservists case, Roger D. Monroe sued his employer, Standard Oil Co. of Ohio, under the Vietnam Era Veterans' Readjustment Allowance Act of 1974, which provides that any employe shall not be denied his job or promotion "or other incident or advantage of employment" because he is in the reserves.

Monroe said when he was required to attend his reserve unit for a weekend he was sometimes able to switch work schedules with other employes. But when he could not, the company refused to allow him to work overtime or on other days to make up for the time lost. The company, however, provided him with leaves of absense for that time and did pay him for the two weeks of duty in the summer, a Standard Oil spokesman said.

The court held that Congress in drafting the veterans act intended to protect employe reservists from discrimination such as discharges or demotions because of their reserve status. But Congress didn't intend for reservsts to get benefits such as special work schedules.

". . . Congress decided what allowance employers should make to reservists whose duties force them to miss time at work: provide them a leave of absense," the Court said. "If Congress had wanted to impose an additional obligation upon employers, guaranteeing that employe-reservists have the opportunity to work the same number of hours or earn the same amount of pay that they would have earned without absenses attributable to military reserve duties, it could have been done so expressly."

In addition, the court said the law placed certain burdens on employers for which they are not compensated. "The frequent absences from work of an employe-reservist may affect productivity and cause considerable inconvenience to an employer who must find alternative means to get necessary work done," the court said. "Yet Congress has provided . . . that employers may not rid themselves of such inconveniences and productivity losses by discharging or otherwise disadvantaging employe-reservists solely because of their military obligations."

In the mining case, the court ruled that a warrant may not be constitutionally required when Congress feels that warrantless searches are necessary to make a regulation effective and that the owner of the commercial property knows his property will be periodically searched.