Roseland Lake is part of the Little River watershed, which is within the Thames River Drainage Basin. The Little River watershed is 19,393 acres of mostly agricultural land with some undeveloped woods and wetland and some residential development.
The lake is fed by Muddy Brook from the north and Mill Brook from the West and another small stream. The Little River begins at Roseland Lake's only outlet. It drains under Stonebridge Road southward into Sheppard's Pond (also sometimes spelled Shepherd's Pond or Shepard's Pond), which is visible from Little Pond Road. Sheppard's Pond is a natural impoundment.
The Town of Putnam uses Roseland Lake as a drinking water supply. The diversion of water at the Peake Brook Road Water Treatment Plant is located at the Sheppard's Pond dam, approximately between 2.5 to file north of the confluence of Little River and Quinebaug River in Putnam, CT.
The Little River Watershed is mostly rural, with an estimated:
Since 1985, the developed areas and grass cover have increased, while forested areas have decreased. (Muddy Brook and Little River Water Quality Improvement Plan)
At Roseland Lake, Roseland Park runs along much of the western shoreline. The north shoreline is heavily wooded. The east and south shorelines have light residential development.
Roseland Lake is considered a kettle pond. A kettle pond is a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters.