Tomh is correct. The grade is not reasonable for asphalt shingles. The rubber may not need replacing, or it may. Taking up the rubber might be impossible Amit. The stuff might have been melted down to the base. Be prepare to remove the boards and the rubber and put down new boards when you do the work, I can't say for certain, but this is a possibility. The other option is that you can possibly apply something over the rubber which is better than trying to remove it. This is where I step off and recommend you consult the pros. I just thought you'd like to hear from an unbiased person who knew about flat roof rules, not necessarily the best way to fix. Actually, the pitch of your roof is 1/10 as stated, but still not adequate for shingles.