material expense or inventory

if you have inventoried the items in prior years you must continue that method unless you file for a change in accounting methods using form 3115.  this is not easy to complete, so you probably should consult a pro.  if you just started the business, 

FROM IRS PUB 334

Keeping inventories. When the production, purchase,
or sale of merchandise is an income-producing factor in
your business, you generally must take inventories into
account at the beginning and the end of your tax year, unless you are a small business taxpayer. If you must account for an inventory, you generally must use an accrual
method of accounting for your purchases and sales.

Inventories
Generally, if you produce, purchase, or sell merchandise
in your business, you must keep an inventory and use an
accrual method for purchases and sales of merchandise.

Exception for small business taxpayers. If you are a
small business taxpayer, you can choose not to keep an
inventory, but you must still use a method of accounting
for inventory that clearly reflects income. If you choose not
to keep an inventory, you won’t be treated as failing to
clearly reflect income if your method of accounting for inventory treats inventory as non-incidental material or supplies, or conforms to your financial accounting treatment
of inventories. If, however, you choose to keep an inventory, you generally must use an accrual method of accounting and value the inventory each year to determine
your cost of goods sold in Part III of Schedule C.
Small business taxpayer. You qualify as a small
business taxpayer if you (a) have average annual gross
receipts of $26 million or less for the 3 prior tax years, and
(b) are not a tax shelter (as defined in section 448(d)(3)). If
your business has not been in existence for all of the
3-tax-year period used in figuring average gross receipts,
base your average on the period it has existed, and if your
business has a predecessor entity, include the gross receipts of the predecessor entity from the 3-tax-year period
when figuring average gross receipts. If your business (or
predecessor entity) had short tax years for any of the
3-tax-year period, annualize your business’ gross receipts
for the short tax years that are part of the 3-tax-year period. See Pub. 538 for more information.
Treating inventory as non-incidental material or
supplies. If you account for inventories as materials and
supplies that are not incidental, you deduct the amounts
paid to acquire or produce the inventoriable items treated
as materials and supplies in the year in which they are first
used or consumed in your operations.

You have a service business and the bulk rolls are consumable supplies  not inventory unless you also sell the supplies for a profit which I doubt you do.  Only items purchased or manufactured for sale/resell are inventory.