Rocky Mountain National Park Wilderness and Indian Peaks Wilderness Expansion Act

Rocky Mountain National Park Wilderness and Indian Peaks Wilderness Expansion Act - Designates certain lands in Rocky Mountain National Park, Colorado, as the Rocky Mountain National Park Wilderness (the Wilderness) and as a component of the National Wilderness Preservation System. Provides for the inclusion of specified potential wilderness land within the Park in such Wilderness.

Sets forth provisions: (1) governing continued operations at the Grand River Ditch; and (2) concerning water rights and permitted and prohibited activities within such Wilderness.

Directs the Secretary of the Interior to establish an alignment line and identify the boundaries for the East Shore Trail within the East Shore Trail Area. Authorizes necessary adjustments in such boundaries, except any that would place any portion of the Trail in such Wilderness. Includes any portion of such Area that is not traversed by the Trail, that is not west of the Trail, and that is not within 50 feet of the centerline of the Trail in such Wilderness.

Amends the Indian Peaks Wilderness Area, the Arapaho National Recreation Area and the Oregon Islands Wilderness Area Act to adjust the boundaries of: (1) the Indian Peaks Wilderness Area; and (2) the Arapaho National Recreation Area.

Applies provisions governing leases of National Park System buildings and property to property known as the Leiffer tract near the Park's eastern boundary in Larimer County, Colorado.