I don't defend Rosa. I defend every manager with athletes busted for doping, because no one of them can have real advantages giving doping to their athletes, since they have more to lose than to earn if their athletes are positive.
The reality, expecially in African Countries (but not only), is that INDIVIDUALS hope to change their level taking doping, and their managers can't control what they do. In the most part of cases, managers are European or American, working with athletes far 10,000 km from the office, and don't have continuous connections with the athletes.
In the case of Rosa, of course it's normal to have doubts, because are really too many the athletes they manage who are positive for doping. But who knows the African reality, knows also that the athletes belong to different groups, not connected one with another, and the problem is that, from Rosa, there is not a direct control of their activity when they are in training at home.
For example, the situation of Global (the management of Jos Hermens) is very different : there are only 3 training camps, with continuous control (the responsible coaches live in the camp with the athletes, and follow on daily basis all the activity
of the athletes), and Global is not interested, and doesn't want, athletes not under one of the official coaches.
Other managements don't have a real technical organization in Kenya, but only put strong athletes under contract, without following (and the most part of times not knowing) their training. In these cases (I don't want to give the name of those managements, but the responsible well know) the managers speak directly with the athletes, who, of course..... are always ready, also when this is not true.
So, I'm sure there is no one manager, working with African athletes, who has active role in doping his athletes, but there are many that are not able to control their athletes, because don't believe (and never tried) in any technical organization, thinking African athletes are so strong that don't need any professional coach.
At the end of every thing, the doped athletes are individual WITHOUT a real coach following them (many Kenyans who say they are coaches of some top athletes really follow the athlete only 2 times per week, and in the case of marathon drive the car giving water during the long runs : so, they are not coaches, but drivers).
Since there is a big disinformation about the reality of Kenyan athletics (only who works and lives there knows the REAL situation), of course everybody is authorized to think there is some organization behind the widespread Kenyan doping, while the reality is that doping is produced by the LACK of organization.