The root note give the letter name to the arpeggio/chord. The dominant 7th part refers to the intervals between the notes. A dominant 7th chord has the root, 3rd, 5th and flat 7th scale degrees in the chords. So a D7 always has the notes D, F#, A, C in it. The D7 arpeggios all follow the note sequence D, F#, A, C but since there are several different places where the D note is found on the neck, there are also different places where you can play a D7 arpeggio.
When you go to a different arpeggio shape it isn't always just an octave higher, but the highest note in the pattern will be higher as you move up the neck. The note order of the arpeggios doesn't change, but the highest and lowest notes are different in the different shapes. In other words, the arpeggios don't always end on the same note, they end on the highest note in the chord that is within the same fretboard area (generally).