One thing to check: if you're using Firefox, is autofill disabled? If not, that might be what's causing the text delay. (Preferences > Privacy and Security > Forms and Autofill: uncheck "Autofill addresses" and "Autofill credit cards." You can leave "Autofill logins and passwords" checked if that's your preference; from what I can tell, that particular setting does not affect Roll20 performance.)