Is there a way we can rollback to previous state of the transaction using ROLLBACK without BEGIN TRANSACTION
?
delete from table1;
ROLLBACK
As SQL server error tells you -- no you can't. And many people would be curious why would you want that in the first place.
Keep in mind SQL server has an implicit transaction -- that is for DML you issue without explicit BEGIN TRAN, SQL server will start and finish a transaction for you behind the screen.
A common usage of ROLLBACK is for error handling. If somewhere in the middle of the transaction you realize you cannot proceed further due to bad user input or other reason -- then a reasonable action is to ROLLBACK to return to the starting point
The worst thing that can happen is leave your data state 'somewhere in the middle'.