It depends on the component you're using:
With roUrlTransfer, which implements the ifUrlTransfer interface, you can use the EnablePeerVerification() method with a parameter value of False.
If you're using any other component, e.g. roVideoScreen, etc, there is no interface I'm aware of that these components implement that will do that.
Of course, you could always put the certificates in your Roku package and call ifHttpAgent.SetCertificatesFile(), or configure your server to not do the validation.