Your problem is a very common one in our area. A major cause of disturbed ground in your spring lawn is the digging and tunneling done by critters such as moles, raccoons , squirrels and skunks. See the link below.
Be careful of rolling lawns this time of year as there are still many soppy, wet areas where rolling might actually do more damage than good. Rolling saturated soils can result in soil compaction. Rolling is popular this time of year to flatten out mole tunnels and mounds and from what I’ve observed, the moles have definitely been active over the winter. However, you should wait to roll after the soil has dried and compaction is less likely, i.e. after you have some nice green grass growing.
Bumps and rises should to be diagnosed before correction. If caused by an object, it will need to be removed. If a bump is from burrowing animals they will have to be removed before the area can be smoothed. It may be possible to flatten some of the smaller bumps simply by stepping on them.
The lawn is made up of layers, for simplicity, lets say: the soil, roots, thatch, and the blades. Thatch is the area just above the soil, that protects the roots. It is normally about 1/4″-1″ in height of matted decomposing grass clippings and generally dying old grass plants that fade away as new plants are generated. When you have a thin lawn or a disease or insect problem that is weakening an area (think Chinch bugs), the blades go first, then the thatch rapidly decomposes leaving bare soil. This bare area then erodes even deeper with rainfall, wind and activity. That leaves a depression when compared to the surrounding area of healthy lawn. This gives the illusion of a bump. These various layers in the soil tend to freeze and thaw as the weather changes, causing chunks of soil to heave out of the ground.