Certificate installation normally requires that only a intermediate CA certificate (and not roots) to be installed on web servers along with the SSL certificate. Unless your server vendor specifically requires you to install the root CA, you should not install it on your web server. Typically Roots are only installed on Clients browsers in order to grant the Chain of Trust.
These roots are the trust anchor for both SHA1 and SHA2 backwards capable SSL certificates.
You can download the Root CA for your SSL certificate from the below links by brand.
Note: Depending on your SSL certificate brand type you will want to download its own brand root.
If you also require the intermediate CA certificate for your SSL certificate click Here.