It is nearly impossible to find a
reseller hosting account that offers root access. At best, they might show the willingness to provide you access to specific resources that can help accommodate your needs but root access is out of question as of now as there are high risks involved.
If allowed root access, you will be able to access other reseller accounts easily and make far-reaching changes which may not really be a desirable situation for any reseller server hosting service. If you need root access, the best option is to go for
VPS hosting or
dedicated server hosting.