Roxann joined the Rogue Rage team because she, her partner and several friends started mountain biking last year, with a preference for riding trails and exploring areas of Manitoba.
I'm quite unclear about what exactly you are attempting to show as the cause of her joining the team.
Did Roxann join the team because she started mountain biking last year, or because she started mountain biking with her partner and several friends, or because she has a year's experience, or because her preference is for mountain biking in Manitoba?