The db_securityadmin role is not required. However, the db_ddladmin role is required to execute cs_system_GenerateSectionTotals, cs_system_GenerateTagCounts, and cs_system_GenerateWeblogYearMonthDayList stored procedures. These procedures are used by CalculateSectionTotalsJob, CalculateTagCountsJob and GenerateWeblogYearMonthDayListJob tasks, respectively.
It is possible you could disable these jobs in the tasks.config and set up one or more SQL Server Agent jobs to execute these procedures.