Progressives of both parties, including Roosevelt, were the original big-government liberals. They understood full well that the greatest obstacle to their schemes of social justice and equality of material condition was the U.S. Constitution as it was originally written and understood: as creating a national government of limited, enumerated powers that was dedicated to securing the individual natural rights of its citizens, especially liberty of contract and private property.
Looking ahead, conservatives hardly need to look back to progressives for inspiration. If there is a desire to "conserve" or restore something about our political tradition that has been lost with the rise of modern liberalism, how about the American founding as a model? It is with the founders that we can find the patriotic promotion of America as an exceptionally great nation -- a notion that attracts some conservatives to TR.