Snare drum music is written on a traditional music staff. The music staff has five lines and four spaces. The snare drum is indicated by placing a line note on the third line of that staff (or stave)
Read snare drum rhythm the same way you read traditional music notation. There are eighth notes, sixteenth notes, and quarter notes. You don't have sharp or flat notes in marching band drum music. Drum music doesn't indicate pitch and tone.
Understand cross-sticking notation. When a small x is placed in the space occupied by the circle of a note, this indicates to use the cross-stick playing method. Cross-sticking is when the drummer crosses one hand over the other to play the snare drum. This produces a specific effect and should be followed.
R and L notated under a note indicates right or left hand. A caret with the narrow point facing right and placed above a note dictates to play that particular beat with more accent.
Drum rolls for snare marching band are indicated by notes placed on other lines and spaces on the music staff and set in quicker note patterns (sixteenth notes), ending on a quarter note.