The degree of public attention paid to Franklin D. Roosevelt's centenary has turned out to be more significant than the event itself. The extra surge of interest has risen from a circumstance that no one anticipated as little as two years ago. It is the presence in the White House of a Republican who openly admires the leadership exemplified by the Democratic FDR - but would exercise it to take the country in a different direction. By calling for his ''new federalism'' in the very week of the Roosevelt anniversary, President Reagan added a nudge to the valuable educational process of considering his proposals in the light of history.
To be sure, many Americans remember the Roosevelt years. But there are younger generations who can learn from the centennial evocations of challenge, hope, and controversy in hard times that were so much worse than later experience for most Americans.An Ivy League historian recalls waves of interest in the FDR era by students who ''wanted to know what made their fathers so mad.'' Yet, for all the disagreement over the New Deal measures, recent polls of historians have placed Roosevelt just behind Lincoln and Washington among the nation's three greatest presidents. Whatever the mistakes which FDR was so ready to risk, he provided a model of leadership responding to individual as well as national needs and acting vigorously to meet them.
This much of the Roosevelt mantle would be claimed by Mr. Reagan. He parts company with certain New Deal federal programs - not with a centerpiece like social security - as being carried on too long for the good of their recipients. One of his fruitful themes in the current Roosevelt-Reagan discussion is that there must be a transition from temporarily needed government aid to the private ability to take care of oneself. FDR, indeed, is said not to have expected emergency measures to continue indefinitely. The present exercise in historical perspective should help the public join Congress, the White House, and the other levels of government in choosing which measures are still worth retaining - and whether they can be most effectively funded and carried out by federal, state, or local jurisdictions.
There can hardly be argument over the FDR prescription which Mr. Reagan cited so fervently in accepting his party's presidential nomination: ''that government of all kinds, big and little, be made solvent and that the example be set by the President of the United States and his Cabinet.'' Nor should there be disagreement over the kind of Roosevelt goal that won Mr. Reagan's vote in the past though he has his own ideas on how to achieve it now: ''The test of progress is not whether we add more to the abundance of those who have much. It is whether we provide enough for those who have too little.''
A legacy of such aspirations, as the past week's utterances suggest, overshadows the decades of squabbling over what kind of elaborate memorial to construct for Franklin Roosevelt. It was in keeping for him to ask for no more than the plain, unornamented block of stone the size of his desk which stands before the National Archives. His monument exists in the life and history of his nation - the more so at the moment as a new President's program invites debate and evaluation of it all over again.