First of all, welcome to Talkbass.
Second of all - there are a lot of different ways to play a bass guitar. The plucking hand, when playing, can use various techniques to create noise, and the way that your roommate has suggested is one of them. It's not common, but it is possible to do.
Some of the more common plucking hand techniques include:
- Fingerstyle playing. Using anywhere from one digit to four digits on the plucking hand, you play notes on the strings, generally alternating your fingers. Muting the lower strings (the ones closest to the ceiling, when in playing position) can be accomplished with the thumb on the plucking hand. Using two fingers is arguably the most common technique.
- Pick playing. Using a plectrum, similar to guitar players, you play notes on the strings, generally alternating between downstrokes and upstrokes with the pick. Muting can be accomplished in different ways with this technique.
- Slapping/popping. The thumb strikes the string, creating a percussive, forceful attack (the slap). The index finger on the plucking hand generally hooks under the string and lets it snap against the fretboard, creating a similarly bright sound (the pop).
- Thumbstyle playing. Using only the thumb from the plucking hand, notes are played on the strings. The palm of the plucking hand can be used to partially mute the strings that are being played, changing the sound.
There are other techniques that involve the plucking hand, but these are likely the most common ones.
While what your roommate is doing isn't specifically
wrong, there are other ways to play the bass guitar that will be more conducive to the music that you will hear and likely want to play. If, at some point, you do decide to use your roommate's method (or if you decide to play that way from the outset) make sure that you have a plan for muting ringing strings. (Also, note that your roommate's method does naturally lend itself to playing chords on bass and may work well for classical music, if that's what you're into. However, if you do choose his method, I would suggest learning the other ones listed above as well.)
Again, welcome to Talkbass, good luck with your playing!