Started DFS by running /usr/local/hadoop-1.0.1/bin/start-dfs.sh -rollback
When you upgrade from v1 to v2, you do it by running start-dfs.sh -upgrade on v2. After upgrade, to rollback, you have to do start-dfs.sh -rollback on * v1 * version of the software and not * v2 * as you have done here. That is the reason why you are seeing the problem.
We should still log a bug on why rollback was allowed from 1.0.1, which rolled back to namenode state from 0.20.203.