This is a fantastic question! If you want to host both sites on the same port (i.e. 443) so that they can be accessed at something like https://mysite.com/rsconnect/ and https://mysite.com/wordpress/ , then you will almost certainly need a "reverse proxy." Another option would be https://mysiteone.com and https://mysitetwo.com, which DNS and a reverse proxy can take care of routing to the appropriate service. The most common examples are Apache and nginx, and there are lots of tutorials that explain using them for SSL termination / routing / etc.
For instance, there are examples in this section of the Connect admin guide: https://docs.rstudio.com/connect/admin/running-a-proxy.html
The other alternative would be to host the products on different ports and manage the SSL termination within each product. I'm not sure how this is done within WordPress, but this section talks about browser security with RStudio Connect, and the SSL certificate can be configured directly. In this setup, your services might be accessed at https://mysite.com (for WordPress) and https://mysite.com:3939 (for RStudio Connect).