I cannot eat root vegetables. What should I do?

It is absolutely ok. You can still fast. You can make other juices that do not contain root vegetables (like beetroot or carrot). Below are some juices that you can have as a Jain - 

• Ash gourd juice
• Bottle gourd juice
• Coconut Water
• Green juice (cucumber, green leafy veggies, and mint)
• Cucumber juice
• Celery juice mixed with a little bit of apple and lemon