WASHINGTON - At least three major Indian cases are waiting for the first session in October of what would be the Roberts court, if Judge John Roberts Jr. receives Senate confirmation as chief justice of the United States.

The nine Supreme Court justices are scheduled to hear oral arguments in a reservation tax case from Kansas. They will also decide whether to take up a crucial land claims case from New York and a challenge from Rhode Island to the constitutionality of the Interior Department;s land-into-trust process.

As the new chief justice - a very high probability - Roberts could put an immediate stamp on the next generation of Indian law. (The decisions could also be a swan song for the two justices with the most direct exposure to tribal jurisprudence: Sandra Day O'Connor, who is trying to retire, and John Paul Stevens, who is 84. Both O'Connor and Stevens were guests on a historic tour of tribal courts several years ago and actually participated in some sessions.)

Ironically, more might be riding on whether the Supreme Court decides to add the two new appeals to its docket than on how it decides the Kansas tax case. The federal circuit courts for both New York and Rhode Island recently made significant rulings affecting all Indian country, and if the Supreme Court declines to review them, they will stand as final. Although the Kansas case raises central issues, it could also turn on narrow grounds.

The Kansas case is now styled Joan Wagnon v. Prairie Band Potawatomi Nation. (Wagnon replaced the previous petitioner, Stephen S. Richards, as secretary of the Kansas Department of Revenue.) The state of Kansas is trying to levy a motor fuel tax on a non-Indian distributor to a tribally owned gas station. The 10th Circuit Court of Appeals invalidated the tax based on a balancing test of state, federal and tribal interests.

The state would like a ''bright line'' rule allowing it to tax non-Indians on and off the reservation, but the court could go either way without making a major change in law.

The Narragansett Tribe of Rhode Island has just won a major victory in the 1st Circuit Court of Appeals rehearing of Carcieri v. Norton. (Rhode Island Governor Donald C. Carcieri and the town of Charleston are actually suing Interior Secretary Gale Norton over 31 acres she placed into trust for the Narragansett Tribe's elderly housing project.) On Sept. 13, a three-judge panel reaffirmed its earlier ruling upholding the land-into-trust process. It rejected the state's claim that the 1934 Indian Reorganization Act made an unconstitutional delegation of power. Furthermore, in a significant holding for all Indian country, it said the act applied to tribes that were recognized after 1934. And two of the three judges said the tribe would have full sovereignty over the new trust land.

The ruling followed within a week of a similar decision by the 8th Circuit Court in a South Dakota case. The agreement in separate circuits removes pressure on the Supreme Court to take up the case.

The Cayuga Indian land claim case in New York state is another matter. The 2nd Circuit on Sept. 9 declined to rehear a July 28 decision throwing out the decades-old case, which had already been won by the tribe in U.S. District Court. The 2 - 1 ruling made a ''novel'' application of an equity principle called ''laches.'' Although frequently described in the press as saying the Cayugas had ''waited too long,'' the decision actually set up a far more complicated legal situation that would also hamper the U.S. government's ability to enforce its laws. Lawyers for the Cayugas say their chance of getting a Supreme Court review is far above average.