If you have another antivirus program, such as WebRoot SecureAnywhere, installed on your PC, Microsoft Defender Antivirus (which includes real-time protection) will automatically disable itself to avoid conflicts between the two antivirus solutions. Therefore, you do not need to enable real-time protection in Microsoft Defender if you are using WebRoot, as it is designed to provide protection on its own.
However, it is important to ensure that your antivirus software is up to date and functioning properly to keep your PC safe. If you are confident in WebRoot's capabilities and it is actively protecting your system, you should be safe without enabling Microsoft Defender's real-time protection.
If you ever decide to uninstall WebRoot or if it becomes inactive, you should then enable Microsoft Defender's real-time protection to ensure continuous protection against threats.