In all states, if you wish to file for Corporation or Limited Liability Company as a new business entity, the name of the entity sought to be formed must be distinguishable from any entity already of record.
So, for instance, if you wish to file for a corporation in Illinois named “Shingled Roofs,” but that name is already used by a filed entity, the name will NOT be available for your use.
However, using additional words (e.g. “by Jim”) in the company name *MAY* be sufficient to make the name distinguishable from the entity already formed. But such a determination is left up to the office of the Secretary of State.
Also note, if the additional words (e.g. “by Jim”) are required to make the entity filing acceptable to the Secretary of State, the business should be operated under that full corporate name only. For example, “Shingled Roofs by Jim, Inc.” should be used in its entirety, rather than just the first part of the corporate name. Using only a part or portion of the corporate name could cause the owners to be subject to personal liability for confusing use of the existing registration.
You may wish to check with your Secretary of State to determine whether or not your state allows you to obtain permission from the current “Shingled Roofs” entity to use a similar name. If they do, you may be able to obtain consent in writing from that existing entity to use the similar name and then file the written consent along with the articles of incorporation that contains the similar name.