Should I purchase an antivirus to go along with Webroot

Hi davevalley
 
Welcome to the Community Forums.
 
No, there is absolutely no need to purchase an antivirus solution to accompany WSA...as and anti malware application WSA covers viruses as well as:
 

• Spyware
• Anti-Ransomware
• Phishing Attacks
• Identity Theft
• Social Network Threats
• Unsafe Websites

In other words you are well protected against what the nasties out there have to throw at you. Please take a look at the diagram below for more information on how the Webroot protection works:
 

 
Now, that is not to say that you could not run additional security software if you wanted to have a layered defence...WSA palys well with just about every other major security app out there...but there is no real need to do that unless you chose to.
 
Hope that helps? But if you have any further questions please do not hesitate to ask.
 
Regards, Baldrick