Why does Novartis own Roche?

Could you please clarify the context of your question? It's not typically expected that Novartis, a pharmaceutical company, would own Roche, another major pharmaceutical company. It's more likely that there may be some confusion or misunderstanding here. Could you perhaps provide more information or context about why you believe Novartis owns Roche, or perhaps you meant to ask about a different aspect of their relationship, such as business partnerships, collaborations, or shared interests? It would help me provide a more accurate and informative response.