It's almost impossible to know for sure the direct impact on mainstream America in the immediate sense. Roosevelt surely had more positive impact than any President since the Civil War, however. His reforms in the food and drug industry, including the Meat Inspection Act and the Pure Food and Drug Act, improved consumer safety in these areas, but it was only a start to really cleaning up industries so it's hard to say how many lives those reforms improved or saved.
In one example of direct economic impact, Roosevelt took the unprecedented step of government intervention into the Coal Strike of 1902 in Pennsylvania. He sent in a federal mediator and gave them 24 hours to strike a deal with workers before he would send in National Guard troops to run the mine. This was the first of many things Roosevelt would do to anger big business, and the miners received a 10% wage increase.
I also think that Roosevelt's creation and expansion of a National Park system, preserving such national treasures as the Grand Canyon and the Redwoods of California, improved the qualitative lives of Americans for succeeding generations as well.